Glossary - More on NUMBER NEEDED TO TREAT (NNT)

Number Needed to Treat (NNT)

Definition
The NNT is the number of patients who need to be treated in order to prevent one additional bad outcome. It is the inverse of the Absolute Risk Reduction (ARR).

At a Glance

Definition

How to Calculate NNTs

Sample Calculation

Practice Calculation

Table of Examples

Nominate Additional NNTs

How to Calculate NNTs

NNT = 1/ARR
ARR = |CER - EER|

where

CER = control group event rate
EER = experimental group event rate

Sample Calculation
The results of the Diabetes Control and Complications Trial^* into the effect of intensive diabetes therapy on the development and progression of neuropathy indicated that neuropathy occurred in 9.6% of patients randomised to usual care and 2.8% of patients randomised to intensive therapy. The number of patients we need to treat with the intensive diabetes therapy to prevent one additional occurrence of neuropathy can be determined by calculating the absolute risk reduction as follows:

ARR = |CER - EER| = |9.6% - 2.8%| = 6.8%
NNT = 1/ARR = 1/6.8% = 14.7 or 15

We therefore need to treat 15 diabetic patients with intensive therapy to prevent one from developing neuropathy.

*(Ann Intern Med 1995; 122:561-8)

Practice Calculation
In a randomised controlled trial^* looking into the long-term outcome for stroke patients treated in stroke units (SU) compared with patients treated in general wards (GW), the mortality rate 5 years after the onset of stroke was 59.1% in the patients treated in SU and 70.9% in those treated in the GW. How many patients need to be treated in stroke units to prevent one additional death?

NNT = _______
(If you want to compare your answer with ours, click here.)

*(Stroke 1997; 28:1861-6)

Table of Examples

CONDITION OR DISORDER INTERVENTION vs. CONTROL OUTCOME FOLLOW-UP DURATION EVENT RATES % NNT (95% CI)

CER EER

Primary Care
Chronic fatigue syndrome¹; Patients reporting fatigue (medically unexplained, lasting ³6 months) Cognitive behaviour therapy vs. orthodox medical care Improved function 6-7 months 26.7 73.3 3
(2 to 5)

Mental Health
Major depression² Repetitive transcranial magnetic stimulation (rTMS) vs. sham rTMS ³50% reduction in scores on the Hamilton Depression Rating Scale or Montgomery-Asberg Depression Rating Scale 2 weeks 25 49 5
(3 to 466)

Oncology
Breast cancer³; Postmenopausal women with breast cancer Radiotherapy plus tamoxifen vs. tamoxifen alone Recurrence (both locoregional recurrence and distant metastasis) 10 years 60 47 8
(6 to 13)

Primary Care
Head lice⁴; Patients of any infected with live lice Pediculicides (e.g., permethrin) vs. placebo Freedom from viable lice or eggs 14 days 5.9 97 2
(1 to 2)

Cardiology
Acute myocardial infarction⁵ Angiotensin-converting enzyme (ACE) inhibitors vs. placebo Mortality 30 days 7.6 7.1 210
(125 to 662)

Cardiology
Acute myocardial infarction⁵ Angiotensin-converting enzyme (ACE) inhibitors vs. placebo Nonfatal heart failure 30 days 15.2 14.6 165
(111 to 488)

Infectious Diseases
AIDS⁶; Patients with HIV-1 infection and CD4⁺ lymphocyte count £ 100/mL Ritonavir vs. placebo AIDS-defining illness or death Median 28.9 weeks 37.5 21.9 6
(5 to 10)

Infectious Diseases
AIDS⁶; as above Ritonavir vs. placebo Death from any cause Median 51 weeks 23 16 14
(9 to 43)

Cardiology
CardiologyChronic heart failure (CHF)⁷ b-blockers vs. placebo Hospitalisation for CHF 7 months 17 13 24
(16 to 51)

Cardiology
CardiologyChronic heart failure (CHF)⁷ b-blockers vs. placebo All-cause mortality 7 months 12 9 40
(24 to 149)

Geriatric Medicine
Nonvertebral fractures in community living elderly persons⁸ Calcium and Vitamin D Supplementation vs. placebo Nonvertebral fractures 3 years 13 6 15
(8 to 12)

CONDITION OR DISORDER INTERVENTION vs. CONTROL OUTCOME FOLLOW-UP DURATION EVENT RATES % NNT (95% CI)

CER EER

Cardiology
Congestive heart failure¹ Spironolactone vs. placebo Mortality 24 months 46 35 9
(7 to 16)

Cardiology
Non-Q-wave coronary events (unstable angina or non-Q-wave MI)² Enoxaparin vs. unfractionated heparin Composite end point of death, MI or recurrent angina 14 days 19.7 16.6 31
(17 to 191)

Cardiology
Coronary events in healthy persons with low HDL cholesterol levels³ Lovastatin vs. placebo First acute major coronary events and adverse events 5.2 years 6 4 50
(33 to 97)

Cardiology
Cardiovascular events in treated hypertension⁴ Aspirin vs. placebo Major cardiovascular events 3.8 years 3.9 3.4 176
(90 to 3115)

Myocardial infarction (MI) 1.4 0.9 208
(127 to 551)

Cardiology
Myocardial infarction and average cholesterol levels in older patients⁵ Pravastatin vs. placebo Major coronary events 5 years 28.1 19.7 11
(8 to 24)

Stroke 7.3 4.5 34
(22 to 333)

Death from coronary artery disease 10.3 5.8 22
(15 to 53)

Coronary artery bypass grafting 11.0 6.6 21
(15 to 56)

Cardiology
Chronic heart failure (CHF)⁶ Exercise vs. no exercise Death 3.4 years 40.8 18 5
(3 to 21)

All cardiac events 75.5 34 3
(2 to 5)

Hospitalization for CHF 28.6 10 6
(3 to 32)

Cardiology
Severe vasovagal syncope;
patients with ³6 syncopal episodes and a positive tilt-table test result with syncope or presyncope and relative bradycardia⁷ Pacemaker vs. usual care First recurrence of syncope 2 years 70.4 22.2 3
(1 to 5)

Cardiology
Congestive heart failure⁸ Home-based intervention vs. usual care Proportion of patients with the combined end point of unplanned readmission or out-of-hospital death 18 months 81.3 67.3 Not significant

Out-of-hospital death 18.8 4.1 7
(3 to 44)

Endocrinology
Graves Hyperthyroidism ⁹ Radioiodine and prednisone vs. radioiodine therapy Development and improvement of opthalmopathy 1 year 15 0 7
(5 to 11)

Endocrinology
Type 2 diabetes mellitus in overweight patients¹⁰ Metformin vs. conventional treatment Diabetes related end point 10 years 39 29 10
(6 to 29)

Deaths from diabetes 13 8 19
(10 to 138)

All cause mortality 22 15 14
(8 to 67)

MI 18 11 16
(9 to 78)

EndocrinologyDiabetic men with erectile dysfunction¹¹ Sildenafil vs. placebo Improved erections 12 weeks 10.2 56.5 3
(2 to 3)

Gastrointestinal
Endoscopic re-treatment of bleeding peptic ulcer¹² Endoscopy vs. surgery Mortality at 30 days, duration of hospitalization after treatment, ICU stay, need for blood transfusion and treatment-related complications 6 weeks 36 15 5
(3 to 25)

Geriatrics
Nonvertebral fractures and bone loss¹³ Calcium and vitamin D vs. placebo Nonvertebral fractures 3 years 13 6 15
(8 to 12)

Geriatrics
Alzheimer disease¹⁴ Donepezil vs. placebo Nausea 12 weeks 8 22 8
(5 to 17)

Insomnia 5 18 9
(6 to 18)

Diarrhea 3 13 10
(6 to 20)

Hematology
Stroke in children with sickle-cell anaemia; periodic blood transfusions¹⁵ Transfusion vs. standard care All strokes 20 months 16 2 7
(4 to 18)

Cerebral infarction 15 2 8
(5 to 22)

Hematology
Idiopathic venous thromboembolism¹⁶ Warfarin vs. placebo Recurrent venous thromboembolism 3 months 20.5 1.3 6
(3 to 9)

Total bleeding 1.2 11.4 10
(5 to 30)

Infectious Diseases
Herpetic gingivostomatitis¹⁷ Acyclovir vs. placebo Oral lesions 8 days 70 6.5 2
(1 to 2)

Eating difficulties 47 6.5 3
(2 to 5)

Drinking difficulties 30 3.2 4
(2 to 11)

Infectious Diseases
HIV infected persons with previous antiretroviral treatment¹⁸ Indinavir, zidovudine + lamivudine vs. zidovudine + lamivudine Changes in HIV RNA levels and CD4+ cell counts. 24 weeks 0 90 2

Infectious Diseases
Shigellosis in Bangladeshi children¹⁹ Vitamin A vs. no vitamin A Clinical cure by day 5 5 days 20 45 4
(2 to 18)

Bacteriological cure from day 3 39 38 Not signific-atnt

Infectious Diseases
HIV infection; breast-fed infants²⁰ Zidovudine vs. placebo HIV-1 infection in the live-born children of women in the study 6 months 27.5 18 11
(6 to 100)

Mental Health
Children and adolescents with non-psychotic major depressive disorder²¹ Fluoxetine vs. placebo Improvement 8 weeks 33 56 5
(3 to 33)

Mental Health
Bipolar disorder; manic relapse²² Training plus routine care vs. routine care alone Manic relapse 18 months 57 27 3
(2 to 16)

Mental Health
Major depression²³ Slow, repetitive transcranial magnetic stimulation (rTMS) vs. Sham rTMS Severity of depression 2 weeks 25 49 5
(3 to 466)

Neurology
Alcohol-related seizures²⁴ Lorazepam vs. placebo Occurrence of a second seizure 6 hours 24 3 5
(4 to 9)

Neurology
Care for acute stroke victims²⁵ Patients were allocated to a Stroke unit or to Ward care Proportion of patients living at home 5 years 18.2 34.5 6
(4 to 21)

Neurology
Migraine headaches²⁶ Riboflavin vs. placebo Frequency of headaches 3 months 19 54 3
(2 to 11)

Headache days 15 57 3
(2 to 6)

Neurology
Acute stroke unit care²⁷ Stroke unit vs. general ward care Quality of life measured by the Frenchay Activity index ³ 30 points 5 years 40.6 5
(2 to 80)

Hematology
Reducing venous thromboembolism after elective neurosurgery²⁸ Enoxaparin vs. placebo Pulmonary embolism (PE) or deep venous Thrombosis (DVT) 8 days 33 17 7
(4 to 18)

PE or proximal DVT 14 5 12
(6 to 73)

Overall DVT 32 17 7
(4 to 20)

Proximal DVT 13 5 13
(7 to 143)

Neurology
Non-disabling stroke; carotid endarterectomy²⁹ Carotid endarterectomy vs. medical care Ipsolateral stroke 5 years 18.7 13.1 18
(10 to 186)

Any stroke 26.4 19.8 15
(8 to 100)

Stroke or death 36.4 27.9 12
(7 to 44)

Disabling stroke or death 20.1 14.9 19
(10 to 783)

Neurology
Multiple sclerosis attacks³⁰ Methylpredni-solone vs. placebo ³ 1 point improvement on Kurtzke Expanded Disability Status Scale 1 year 22 50 4
(2 to 105)

Neurology
Secondary progressive multiple sclerosis³¹ Interferon-b1b vs. placebo Progression 33 months 49.7 39.1 9
(6 to 30)

Obstetrics-Gynecology
Excessive uterine bleeding³² Levonorgestrel intrauterine system vs. control group Number of women canceling their decision to have a hysterectomy 6 months 14 64 2
(1 to 4)

Oncology
Stages II and III breast cancer³³ Adjuvant chemotherapy + radiotherapy vs. chemotherapy alone Locoregional recurrence 10 years 26 5 5
(4 to 6)

Oncology
Locally advanced prostate cancer³⁴ Radiotherapy + goserelin vs. radiotherapy alone Death 5 years 28 17 10
(5 to 34)

Oncology
Acute myeloid leukemia; autologous bone-marrow transplantation after intensive chemotherapy³⁵ Bone-marrow transplantation vs. no further treatment Relapse 7 years 53 34 5
(3 to 11)

Relapse or cancer-specific death 57 45 9
(5 to 80)

Death 49 40 Not significant

Oncology
Breast cancer; preservation of the intercostobrachial nerve during axillary node clearance³⁶ Preservation vs. sacrifice of the intecostobrachial nerve Some sensory deficit 3 months 84 63 5
(3 to 24)

Oncology
Breast cancer³⁷ Radiotherapy plus tamoxifen vs. tamoxifen alone All recurrences 10 years 60 47 8
(6 to 13)

Locoregional recurrence with or without distant metastases 35 8 4
(4 to 5)

Ophthalmology
Second-eye cataract surgery³⁸ Surgery vs. control Difficulty reading normal print 6 months 35 6 4
(3 to 6 )

Eyesight prevented most activities 11 0 10
(6 to 23)

Below-average overall vision 18 0 6
(4 to 10)

Eyesight interfered greatly in life 26 1 5
(3 to 7)

Stereoacuity worse than 3000-sec arc 70 12 2
(2 to 3)

Orthopedics
Painful stiff shoulder³⁹ Corticosteroid injections vs. physiotherapy Treatment success 1 year 46 77 3
(2 to 8)

Pediatrics
Acute otitis media (AOM)⁴⁰ Xylitol syrup vs. control syrup Incidence of AOM 3 month 41 29 8
(4 to 53)

Xylitol gum vs. control gum 28 16 9
(5 to 36)

Xylitol lozenges vs. control gum 28 22 Not significant

Peripheral vascular surgery
Acute arterial leg occlusion⁴¹ Thrombolysis vs. surgery Amputation- free survival at 6 and 12 months 6 and 12 months 6 months: 25.2
12 months: 30.1
6 months: 28.2
12 months: 35
Not significant

Hemorrhagic complications 5.5 12.5 14
(8 to 47)

Respiratory
Acute asthma⁴² Budesonide vs. placebo Relapse 21 days 25 13 9
(5 to 179)

Respiratory
Chronic obstructive pulmonary disease (COPD)⁴³ Glucocorticoids vs. placebo First treatment failure (death, need for intubation and mechanical ventilation, readmission for COPD, or intensification of drug therapy) 1 and 3 months 1 month: 33 1 month: 23 10
(5 to infinity)

3 months: 48 3 months: 37 9
(4 to infinity)

Rheumatology
Calcific shoulder tendinitis⁴⁴ Pulsed ultrasound vs. sham therapy Changes from baseline in shoulder calcium deposits on radiography, pain, active range of motion and power of shoulder and activities of daily living were assessed. 9 months 8 42 3
(2 to 9)

Urology
Benign prostatic hyperplasia⁴⁵ Finasteride vs. placebo Surgery for BPH 4 years 10.1 4.6 18
(13 to 27)

Acute urine retention 6.6 2.8 27
(19 to 43)

Remission rates in active Crohn disease⁴⁶ Budesonide vs. mesalamine Remission 16 weeks 36 62 4
(3 to 10)

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates
% NNT
95% CI

CER EER

Cardiology
Coronary Heart Disease¹ Patients invited to attend nurse led secondary prevention clinics vs. Patients who received regular care Presence, frequency and course of chest pain 12 months 11 7 24
(16 to 170)

Hospital admissions 28 20 13
(9 to 35)

Endocrinology
"Insulin requiring" diabetes² Regular telephone contact with a diabetes nurse educator for advice about adjustment of insulin therapy vs. regular clinic visits and usual contact with the endocrinologist for insulin adjustment Mean HbA_lc level and proportion of patients who achieved a reduction in HbA_lc level ³ 10% 6 months 35 87 2
(1 to 4)

General Surgery
Hip and knee arthroplasty³ Patients were allocated to a clinical pathway group (received "proactive" treatment where specific daily goals were set for the patient) vs. control group (received "reactive" treatment where the healthcare team provided care in response to the patient's conditions and wants) Complications (wound infection, chest infections deep venous thrombosis, joint dislocation, decubitus pressure areas, failure to cope at home and decreased range of motion after discharge) 3 months 28.2 10.9 6
(4 to 19)

Geriatrics
Non-vertebral fractures and bone loss in the elderly⁴ Elemental calcium + vitamin D vs. placebo Non-vertebral fractures verified by radiographs or hospital records 3 years 12.9 5.9 15
(8 to 12)

Infectious Diseases
Sexually transmitted diseases in minority women⁵ Behavioral intervention (3 weekly group sessions in which recognition of risk, commitment to change and acquisition of skills were discussed) vs. control group (received 15 minutes of standard individualized counseling by nurse clinicians according to guidelines from the US Centers for Disease Control and Prevention) Subsequent infection with Chlamydia trachomatis or Neisseria gonorrhoeae, assessed by testing endocervical samples with DNA probes 6 and 12 months 26.9 16.8 10
(6 to 32)

Respiratory
Children with asthma⁶ Structured discharge packages vs. usual discharge packages at the time of discharge Readmission to hospital 6 months 38 15 5
(3 to 12)

Respiratory
Smoking cessation; using a nicotine inhaler⁷ Nicotine inhalers vs. placebo Self reported abstinence from smoking (verified by laboratory measurements) 1 year 18 29 10
(5 to 483)

Respiratory
Smoking cessation rates⁸ Intensive intervention (which includes a 30 minute behavioral counseling session given by nurses, a videotape from the American Heart Association and an audiotape of relaxation exercises vs. usual care (which includes printed material and a list of partially subsidized outpatient cessation programs) Confirmed smoking cessation 12 months 20 27 16
(9 to 52)

Respiratory
asthma; effectiveness in treating inner city patients⁹ Educational program vs. conventional asthma care and routine follow-up Attendance at follow up appointments, subsequent ED visits and hospitalization 6 months 27 59 3
(2 to 11)

Urology
Urinary incontinence in women¹⁰ Bladder training or pelvic muscle exercises with biofeedback assisted instruction vs. combined bladder training plus pelvic muscle exercises Frequency of self reported incontinence 3 months 13 31 5
(3 to 23)

Perceived symptom improvement 30 52 4
(3 to 20)

Condition or disorder Intervention vs. control Outcome Follow-up duration Event rates
% NNT
(95% CI)

CER EER

Cardiology
Adults at high risk for cardiovascular events¹ Ramipril vs. placebo Myocardial Infarction, stroke and cardiovascular mortality 4 years 18 14 26
(19 to 43)

Cardiology
Patients surviving Myocardial Infarction who had contraindications to b-blockers² Amiodarone vs. placebo Cardiac mortality 1 year 11 6 23
(12 to 1323)

Arrhythmias 19 8 9
(6 to 16)

Cardiology
Recent-onset atrial fibrillation in patients with or without heart disease³ Oral propafenone vs. placebo Rates of conversion to sinus rhythm at 3 and 8 hours 8 hours 3 hrs:
18 3 hrs:
24 3 hrs: 4
(3 to 6)

8 hrs:
37 8 hrs:
76 8 hrs: 3
(2 to 4)

Cardiology
Patients resuscitated from ventricular arrhythmias; use of implantable cardioverter-defibrillators (ICD) in reducing mortality⁴ ICD vs. antiarrhythmic drug therapy All-cause mortality 18 months 24 16 13
(8 to 30)

Geriatrics
Hip fractures in nursing home patients⁵ External hip protectors vs. control (no hip protector) Hip fracture 1 month 7.4 3.2 24
(13 to 183)

Geriatrics
New fractures in postmenopausal women who had low bone-mineral density and existing vertebral fractures⁶ Alendronate sodium vs. placebo New vertebral fractures confirmed by radiography 3 years < 75 years of age:
13 < 75 years of age:
6 < 75 years of age: 15
(11 to 27)

³75 years of age:
18 ³75 years of age:
11 ³75 years of age: 15
(8 to 21)

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates
% NNT
95% CI

CER EER

Cardiology
Myocardial infarction with cardiogenic shock¹ Immediate revascularization (angioplasty or bypass surgery to be done as soon as possible and within 6 hours of randomization) vs. medical stabilization (intraaortic balloon counterpulsation and thrombolytic therapy with delayed revascularization – minimum 54 hours after randomization) All-cause mortality 6 months 63 50 8
(5 to 66)

Cardiology
Coronary artery disease (CAD) and low levels of high density lipoprotein cholesterol² Gemfibrozil vs. placebo Nonfatal myocardial infarction or CAD death 5 years 21.7 17.3 23
(13 to 74)

Stroke 6.9 5.1 56
(27 to 725)

Cardiology
Acute myocardial infraction (MI)³ Aspirin and heparin plus angioplasty vs. aspirin and heparin plus streptokinase (control) All-cause mortality 5 years 24 13 10
(6 to 35)

Cardiac mortality 20 7 8
8 (5 to 15)

Death and nonfatal MI 22 6 6
(4 to 11)

Cardiology
Unstable coronary artery disease⁴ Dalteparin vs. placebo Death, MI or both at 1 month 6 months 5.8 3.1 37
(23 to 102)

Death, MI or need for revascularization at 3 months 33 29 27
(13 to 208)

Cardiology
Unstable coronary artery disease⁵ Invasive strategy vs. noninvasive strategy Death, MI or both 6 months 12 9 37
(20 to 398)

Cardiology
Medically refractory angina⁶ Transmyocardial revascularization (TMR - consisted of a limited muscle-sparingleft thoracotomy and the creation of transmyocardial laser channels) and continued medication vs. continued medication alone Reduction of ³ 2 angina cases 12 months 11 61 2
(2 to 3)

Cardiology
Congestive heart failure (CHF)⁷ Usual CHF medicine plus low dose of lisinopril (2.5 or 5.0 mg/d-control) vs. usual CHF medicine plus high dose of lisinopril (30 mg/d) Mortality plus hospitalization 3 years 83.8 79.7 26
(16 to 82)

Mortality plus cardiovascular (CV) hospitalization 74.1 71.1 34
(17 to 264)

Mortality Plus CHF hospitalization 60.4 55.1 17
(12 to 37)

CV mortality plus CV hospitalization 72.7 69.4 30
(16 to 281)

Cardiology
Recent-onset atrial fibrillation⁸ Oral amiodarone vs. placebo Rates of conversion to sinus rhythm (verified by Holter monitoring) 24 hours 35 87 2
(1 to 4)

Cardiology
Chronic heart failure⁹ Metroprolol vs. placebo All-cause death or hospital admission 1 year 38 32 17
(12 to 32)

Hospitalization for worsening heart failure 15 10 22
(15 to 39)

Cardiology
Atrial fibrillation (AF)¹⁰ Amiodarone (10 mg/kg of body weight) vs. sotalol or propafenone (control) Time to first recurrence of AF confirmed on ECG 468 days 63 35 4
(3 to 6)

Geriatric Medicine
Postmenopausal¹¹ Alendronate sodium vs. placebo ³1 day of bed rest 3 years 15 11 23
(15 to 56)

³7 days of bed rest 9 4 21
(17 to 32)

³7 days of limited activity 44 41 23
(12 to 308)

Geriatric Medicine
Postmenopausal women with osteoporosis¹² Oral risedronate vs. placebo New vertebral fractures 3 years 16 11 20
(11 to 111)

Non-vertebral fractures 8 5 32
(17 to 250)

General Surgery
Postoperative abdominal wound infection¹³ Impervious wound-edge protector vs. no wound edge protector (control) All wounds 30 days 30 14 7
(4 to 13)

Clean-contaminated wounds (minor interruption in aseptic technique or minor spillage from the gastrointestina 1 tract) 13 7 Not significant

Contaminated wounds (major interruption in aseptic technique or susequent spillage 67 24 3
(2 to 6)

Dirty wounds (gross fecal spillage) 94 75 Not significant

Hematology
Pulmonary embolism and proximal deep venous thrombosis (DVT)¹⁴ Subcutaneous low-molecular-weight heparin (tinzaparin sodium) vs. unfractionated heparin (control) Recurrent venous thromboembolism 3 months 6.8 0 15
(8 to 36)

Major bleeding 1.9 1.0 Not significant

Minor bleeding 2.9 1.0 Not significant

Death 8.7 6.2 Not significant

Infectious Disease
HIV-1-infected patients with tuberculosis¹⁵ Trimethoprim-sulfamethoxazole (co-trimoxazole) vs. placebo Death 10.5 22.6 13.3 11
(7 to 26)

³ hospitalization 12.4 7.6 21
(11 to 172)

Infectious Disease
HIV-1-infection¹⁶ Efavirenz plus zidovudine and lamivudine vs. indinavir plus zidovudine and lamivudine Percentage of patients with suppression of plasma HIV-1 RNA to < 400 copies/mL 48 weeks 48 70 5
(4 to 10)

Mental Health
Depression¹⁷ Fluozetine vs. desipramine (control) Continuing initial medication 12 months 20 42 5
(4 to 10)

Fluozetine vs. imipramine (control) 27 42 7
(4 to 25)

Mental Health
Moderate depression¹⁸ Hypericum extract vs. placebo ³50% improvement in the Hamilton Depression Rating Scale 8 weeks 48 67 6
(3 to 50)

Hypericum extract vs. imipramine 67 76 Not significant

Mental Health
Opioid dependance¹⁹ Methadone maintenance for 14 months vs. 120 days of methadone-assisted maintenance and 60 days of methadone-assited detoxification with intensivepsychosocial serivces and 8 months of aftercare (control) Treatment retention 12 months 55 74 6
(4 to 20)

Neurology
Acute Stroke²⁰ Intra-arterial recombinant prourokinase plus intravenous heparin vs. intravenous heparin alone Proportion of patients with a modified Rankin score £ 2 90 days 25 40 7
(3 to 268)

Neurology
Episodic cluster headache²¹ Verapamil vs. placebo Non-response (= having £ 50% reduction in cluster headache attack frequency) 2 weeks 100 20 1
(1 to 2)

Obstetrics-Gynecology
First-stage labor pain²² Intracutaneous injections of sterile water vs. placebo Labor pain was measured with a 10-cm visual analog scale (0 cm = no pain; 10 cm = worst conceivable pain) 90 minutes 25 59 3
(2 to 13)

Subcutaneous injections of sterile water vs. placebo 25 52 4
(3 to 82)

Oncology
Node-positive prostate cancer²³ Antiandrogen therapy immediately after surgery vs. observation Death 7.1 years 35 15 5
(3 to 34)

Death from prostate cancer 31 6.4 4
(3 to 10)

Any recurrence 82 15 2
(2 to 2)

Oncology
Prostate cancer²⁴ Pelvic floor re-education program (included education about the anatomy and function of the bladder and pelvic floor, active pelvic-floor muscle exercises and biofeedback) vs. placebo program (information about the origin of their incontinence and placebo electrotherapy applied to the abdomen and thighs, but that could not affect pelvic floor function) Incontinence rate at 3 months (continence was defined as a loss of £ 2g of urine on both the 24-hour and 1-hour pad test 1 year 44 10 3
(2 to 6)

Incontinence at 1 year 17 4 8
(4 to 72)

Orthopedics
Lateral epicondylitis (tennis elbow) ²⁵ Local corticosteroid injection of methylprednisolone and lignocaine vs. enteric-coated naproxen Complete recovery at 4 weeks 12 months 5.7 42 3
(2 to 5)

Local corticosteroid injection of methylprednisolone and lignocaine vs. placebo Pain scores £ 3 ate 4 weeks (on 10 point Likert scale) 50 82 4
(3 to 8)

Orthopedics
Osteoarthritis of the knee²⁶ Manual physical therapy and exercise vs. placebo (ultrasonography at a sub-therapeutic intensity Knee surgery 1 year 20 5 7
(4 to 134)

Primary Care
Nosocomial pneumonia²⁷ Semirecumbent body position (45° from the horizontal) vs. supine body position Clinically suspected nosocomial pneumonia 72 hours 34 8 4
(3 to 11)

Microbiologically confirmed nosocomial pneumonia (by bronchoalveolar lavage or protected specimen-brush cultures 23 5 6
(4 to 29)

Primary Care
Influenza²⁸ Oral oseltamivir once daily vs. placebo Laboratory-confirmed influenza-like illness 6 weeks 4.8 1.2 27
(17 to 59)

Oral oseltamivir twice daily vs. placebo 4.8 1.3 29
(17 to 69)

Primary Care
Ventilator-associated²⁹ Invasive management strategy (fiberoptic bronchoscopy to obtain protected specimen-brush samples or bronchoalveolar lavage samples to guide treatment vs. Clinical management strategy (control-clinical evaluation, examination of Gram-stained endotracheal aspirates and adherence to the American Thoracic Society guideline recommendations for choosing antiboitics) All-cause mortality 28 days 26 16 11
(6 to 56)

Pediatrics
Diarrhea incidence in children treated with antibiotics³⁰ Lctobacillus GG vs. placebo Incidence of diarrhea 10 days 26 8 6
(4 to 13)

Stool consistency < 4§ 48 17 4
(3 to 6)

Pediatrics
Acute otitis media³¹ Amoxicillin suspension vs. placebo Persistent symptoms at 4 days 6 weeks 72 59 8
(4 to 72)

Clinical treatment failure at 11 days (persistent fever, earache, crying, irritability or no improvement in appearance of the tympanic membrane) 70 60 Not significant

Pediatrics
Constipation in children³² Cisapride vs. placebo clinical response (>3 spontaneous bowel movements/week with no fecal soiling and no use of other laxtives for ³ 2 weeks) 12 weeks 42 76 3
(2 to 60)

Respiratory
Asthma³³ Asthma clinic vs. standard treatment group Owning a peak flow meter 6 months 56 73 6
(3 to 31)

Waking at night because of asthma 20 7.0 8
(4 to 29)

Rheumatology
Carpal tunnel syndrome³⁴ Injection of methylprednisolone and lignocaine vs. lignocaine alone (control) Symptom improvement-defined as having no symptoms or minor symptoms requiring no further treatment 1 year 7 50 3
(2 to 5)

Rheumatology
Rheumatoid arthritis³⁵ Intravenous infusion of infliximab, 3mg/kg of body weight every 4 weeks vs. placebo Response rate (defined as 20% improvement from baseline according to the 1987 American College of Rheumatology criteria) 30 weeks 20 53 4
(3 to 6)

Intravenous infusion of infliximab, 3mg/kg every 8 weeks vs. placebo 20 50 4
(3 to 7)

Intravenous infusion of infliximab, 10mg/kg every 4 weeks vs. placebo 20 58 3
(2 to 5)

Intravenous infusion of infliximab, 10mg/kg every 8 weeks vs. placebo 20 52 4
(3 to 6)

CONDITION OR DISORDER INTERVENTION vs. CONTROL OUTCOME FOLLOW-UP DURATION EVENT RATES % NNT (95% CI)

CER EER

Cardiology
Ballon angioplasty¹ Routine stent implantation vs. optimal ballon angioplasty with provisional stent Composite end point 6 months 14.9 6.1 11
(7 to 30)

Target vessel Revascularization or surgery 10.1 3.9 16
(9 to 62)

Revascularization or surgery 12.9 5.2 13
(8 to 309)

Cardiology
Unstable coronary artery disease² Invasive strategy (immediate angioplasty and revascularization) vs. non-invasive strategy Death or myocardial infraction (MI) 1 year 14 10 27
(16 to 92)

Death 3.9 2.2 60
(32 to 306)

Readmission 57 37 5
(4 to 6)

Cardiac intervention after discharge 31 8 5
(4 to 5)

Gastrointestinal
Women with irritable bowel syndrome³ Alosetron vs. placebo Relief of abdominal symptoms 1 month 29 41 8
(5 to 22)

Constipation 3 30 4
(3 to 5)

General Surgery
Hip surgery⁴ Aspirin vs. placebo Symptomatic deep venous thrombosis 35 days 1.5 1 232
(140 to 2239)

Pulmonary embolism 1.2 0.7 195
(140 to 466)

Respiratory
Acute-on-chronic obstructive pulmonary disease⁵ Standard treatment plus pressure supported ventilation through a face or nasal mask vs. standard treatment alone Need for intubation After discharge 27 15 9
(5 to 69)

Death 20 10 10
(6 to 98)

Respiratory
Acute respiratory distress syndrome⁶ Lower tidal volumes vs. traditional tidal volumes (control) Death 180 days 40 31 12
(7 to 41)

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates
% NNT
95% CI

CER EER

Mental Health
Depression¹ Fluoxetine plue folic acid vs. fluoxetine plus placebo Clinical response (>50% improvement on the Hamilton Depression Rating Scale 10 weeks 62 82 5
(3 to 30)

Mental Health
Depression² Nurse telehealth care (12-14 calls to each patient during treatment in which the clinic nurse answered questions, offered support and discussed the patient's mental and overall health vs. usual physician care (counselling and treatment with a selective serotonin reuptake inhibitor) ³50% improvement on the Hamilton Depression Rating Scale 6 weeks 37 50 8
(4 to 90)

6 months 38 57 6
(4 to 18)

³50% improvement on Beck Depression Inventory 6 weeks 33 38 Not significant

6 months 37 48 Not significant

Mental Health
Alzheimer's disease³ Family intervention, which comprised 3 sessions of caregiver education, 6 sessions of stress management and 5 sessions of coping skills management vs. interview control group, which comprised of a1 session cathartic interview Caregiver psychiatric morbidity and depression 3 months 85 23 2
(2 to 5)

Family intervention vs. no interview 62 19 2
(2 to 7)

Mental Health
Postpartum depression⁴ Support group (7 psychoeducation a1 visits in which partners participated in 4 out of the 7 visits) vs. control group (7 sessions without partner) Depression status established by the Mini International Neuropsychiatric Instrument 10 weeks 62 19 3
(2 to 15)

Mental Health
Fear of flying⁵ Virtual reality exposure (8 sessions, 4 of which involved information gathering, treatment planning, brief breathing training and cognitive restructuring) vs. waiting list control Proportion of patients who went on a round trip flight at 6 weeks and changes in symptoms (determined from questionnaire) 12 months 7 53 3
(2 to 7)

Standard exposure (8 sessions done at the airport with exposure to pre-flight stimuli and sitting on a stationary airplane with imaginal exposure to takeoffs, cruising and landing) vs. waiting list control 7 67 2
(2 to 4)

Mental Health
Aggression and conduct disorder⁶ Lithium vs. placebo Responders on the Global Clinical Judgments (Consensus Scale) 4 weeks 30 80 2
(2 to 6)

Responders on the Clinical Global Impressions 70 20 2
(2 to 6)

Mental Health
Bulimia nervosa⁷ Cognitive behavioural therapy vs. interpersonal therapy (control) Recovery at 20 weeks 1 year 6 29 4
(3 to 8)

Remission at 20 weeks 28 48 5
(3 to 14)

Normal eating attitudes and behaviours at 20 weeks 27 41 7
(4 to 92)

Mental Health
Post-traumatic stress disorder (PTSD)⁸ Sertraline vs. placebo Response rate (³ 30% reduction from baseline in Clinician Administered PTSD Scale, Part 2 total severity score and Clinical Global Improvement - Improvement (CGI - I) score of 1 or 2) 12 weeks 32 53 5
(3 to 17)

Mental Health
Schizophrenia or schizoaffective disorder⁹ Programme for relapse prevention (education about relapse and how to recognise prodromal symptoms and behaviour, active monitoring, clinical intervention when prodromal episodes were detected and 90 minuets of multifamily psychoeducation groups) vs. usual care Relapse free survival 18 months 66 83 1
(1 to 5)

No hospital admission 61 78 1
(1 to 3)

Mental Health
Chronic depression¹⁰ Nefazodone and psychotherapy vs. nefazodone or psychotherapy (control) Remission (a score of 8 or less on the Hamilton Rating Scale for Depression) or satisfactory response (a reduction in the HRDS by at least 50% from baseline and a score of 15 or less) 12 weeks 48 73 4
(3 to 7)

Mental Health
Acute mania¹¹ Valproate vs. placebo ³ 50% improvement on the Young Mania Rating Scale 21 days 46 70 5
(3 to 15)

Moderate to marked improvement on the Clinical Global Impression Scale 50 68 6
(4 to 74)

Mental Health
Major depressive disorder (MDD)¹² Titrated right unilateral electroconvulsive therapy (RUL ECT) vs. fixed dose RUL ECT (control) Cognitive disturbance (decreased ³ 5 points on the Mini-Mental State Examination) 1-2 days 30 6.7 5
(3 to 22)

Mental Health
Secondary insomnia¹³ Treatment group (4 weekly 1 hour sessions with a therapist involving sleep hygiene instructions, stimulus control and relaxation) vs. control group Clinical improvement (measured by sleep efficiency percentage) 3 months 19 57 3
(2 to 12)

Mental Health
Secondary insomnia¹⁴ Naltrexone plus cognitive behavioural therapy (CBT) vs. placebo plus CBT Drinking relapse (³ 5 drinks/day for men and ³ 4 drinks/day for women) 12 weeks 60 38 5
(3 to 21)

Mental Health
Secondary insomnia¹⁵ Risperidone vs. haloperidol (control) Need for antiparkinsonian drugs 6 weeks 75 50 5
(3 to 10)

Mental Health
Moderate depression¹⁶ Hypericum extract vs. placebo ³ 50% improvement in Hamilton Depression Rating Scale score 8 weeks 48 67 6
(3 to 50)

Hypericum extract vs. imipramine (control) 67 76 Not significant

Geriatric Medicine
Residents in nursing homes¹⁷ Pharmacist medication review vs. no review Deaths from 5 to 8 months (intervention phase) 8 months 9 4 17
(9 to 213)

CONDITION OR DISORDER INTERVENTION vs. CONTROL OUTCOME FOLLOW-UP DURATION EVENT RATES % NNT (95% CI)

CER EER

Dermatology
Intravenous skin antisepsis¹ 0.5% chlorohexidine gluconate (CHG) vs. 70% isopropyl alcohol swab followed by povidone-iodine swab (control) Local catheter related infection 72 hours 12.5 1.2 9
(5 to 23)

CHG vs. povidone-iodine swab followed by 70% isopropyl alcohol swab (control) 9.9 1.2 12
(6 to 48)

Geriatric Medicine
Hip fracture patients with mild to moderate dementia² Intensive geriatric rehabilitation (advice, training, drug treatment, physiotherapy, occupational and speech therapy) vs. control group (discharge to a local hospital) Independent living at 3 months - mild dementia 1 year 67 91 5
(3 to 16)

Independent living at 3 months - moderate dementia 1 year 17 63 3
(2 to 9)

Mental Health
Drug refractory schizophrenia³ Cognitive behavioural therapy (attaining a collaborative understanding of the development of symptoms and working towards reducing distress and disability) vs. befriending (control - sessions focused on neutral topics) ³ 50% improvement in Comprehensive Psychiatric Rating Scale (CPRS) total score 9 months 39 63 5
(3 to 28)

³ 50% improvement in CPRS schizophrenia change scores 50 70 Not significant

Primary Care
Dissolving earwax⁴ Docusate sodium vs. triethanolamine polypeptide (control) Complete visualisation of the tympanic membrane (with or without irrigation) 35 81 3
(2 to 6)

Primary Care
Sepsis⁵ Immune enhancing enteral feeding formula vs. control formula Mortality 32 19 8
(4 to 637)

Acquired bacteraemia 22 8 8
(4 to 28)

³1 acquired nosocomial infection 20 6 8
(5 to 23)

Pediatrics
Routine primary immunisation⁶ Longer needle vs. shorter needle (control) Any local reaction up to 3 days 3 days 84 62 5
(3 to 19)

Redness at 6 hours 66 40 5
(3 to 81)

Redness at 1 day 63 28 3
(2 to 7)

Redness at 2 days 39 9 4
(3 to 8)

Redness at 3 days 28 4 5
(3 to 9)

Swelling at 6 hours 58 23 3
(3 to 6)

Swelling at 1 day 63 28 3
(2 to 7)

Swelling at 2 days 51 19 4
(3 to 7)

Swelling at 3 days 40 13 4
(3 to 10)

Pediatrics
Children with asthma exacerbations⁷ Ward care based on a clinical pathway (comprised a nurse driven protocol for weaning bronchodilators, regular peak flow measurements, asthma teaching, prescriptions for home treatments and coordination of care between the attending physician and private medical doctors) vs. usual ward care Discharge within 24 hours of admission 2 weeks 38 15 5
(3 to 14)

Pediatrics
Acute diarrhea in children⁸ Oral rehydration solution (ORS) vs. standard care Unscheduled follow up visit 10 days 17 11 16
(8 to 481)

ORS use 71 85 8
(5 to 17)

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates
% NNT
95% CI

CER EER

Cardiology
Acute myocardial infarction¹ Coronary stenting plus abciximab vs. intravenous alteplase (control) Composite of death, reinfarction or stroke 6 months 23 9 7
(5 to 36)

Cardiology
Angina and percutaneous transluminal coronary angioplasty² Coumarin and aspirin vs. aspirin alone Composite end point of death, myocardial infarction, target-lesion revascularization and stoke at 30 days 1 year 6.4 3.4 33
(17 to 222)

Composite at 1 year 20 14 17
(10 to 73)

Cardiology
Atrial fibrillation (AF)³ Amiodarone vs. placebo Rates and time to AF or intolerable adverse effects 22 months 88 48 3
(2 to 4)

Sotalol vs. placebo Rates and time to AF or intolerable adverse effects 88 77 Not significant

Cardiology
Patients with cardiovascular disease (CVD) receiving long-term hemodialysis⁴ Vitamin E vs. placebo CDV events 512 days 34 19 6
(4 to 29)

Myocardial infraction 18 8 10
(5 to 230)

Gastrointestinal
Bleeding peptic ulcer⁵ Omeprazole vs. placebo Recurrent bleeding 8 weeks 22.5 6.7 6
(4 to 14)

Hospital stay < 5 days 31.7 46.7 7
(4 to 38)

Geriatric Medicine
Vertebral fractures in men with osteoporosis⁶ Alendronate vs. placebo Incidence of vertebral fractures 2 years 7 1 16
(7 to 56)

Neurology
Multiple sclerosis (MS)⁷ Interferon ß-1a vs. placebo Development of clinically definite MS 3 years 50 35 4
(2 to 8)

Obstetrics-Gynecology
Breech presentation⁸ Planned cesarean section vs. planned vaginal birth (control) Perinatal or neonatal mortality or serious neonatal morbidity 6 weeks 5.0 1.6 30
(20 to 54)

Perinatal or neonatal mortality 1.3 0.3 104
(54 to 416)

Serious neonatal morbidity 3.8 1.4 41
(26 to 90)

Orthopedics
Acute whiplash injuries⁹ Active treatment (gentle, active, small-range and small-amplitude rotational movements of the neck) vs. standard treatment (leaflet providing information about injury mechanisms, advice on suitable activities and instruction on postural correction) No pain 6 months 11 30 6
(3 to 45)

No or low pain 20 44 5
(3 to 22)

Primary Care
Influenza¹⁰ Influenza vaccine vs. placebo Patients reports of fever plus cough or sore throat and associated physician visits and lost work days during influenza period during flu season of 1998-99 After flu season was finished 10.2 1.4 12
(7 to 27)

Pediatrics
Head lice in children¹¹ Malathion lotion vs. bug busting (control) Live lice at 7 days after treatment 7 days 63 23 2
(2 to 6)

Pediatrics
Severe watery diarrhea in children¹² Racecadotril vs. placebo 5 day cure rate 5 days 66 84 6
(4 to 29)

Respiratory
Pulmonary infiltrates¹³ Ciprofloxacin vs. control (physician-directed antibiotics) Mortality 30 days 31 13 Not significant

Resistance or superinfection 38 14 5
(3 to 22)

Cardiology
CAD and hypertension¹⁴ Acarbose vs placebo Major CV events 3.3 years 4.7 2.2 44 (30 to 436)

Cardiology
Myocardial infarction¹⁵ Warfarin + aspirin, warfarin vs aspirin Composite outcomes 1445 days 15% vs 20%, 17% vs 20% 20 (12 to 51), 30 (16 to 483)

Cardiology
Atrial fibrillation¹⁶ Anterior-posterior versus anterior-lateral electrode position Successful cardioversion 24 hours 78 96 6 (4 to 19)

Cardiology
chronic heart failure¹⁷ Candesartan 4 or 8 mg vs placebo All-cause mortality 37.7 months 25 23 46 (26 to 463)

Cardiology
acute myocardial infarction¹⁸ Coronary angioplasty vs fibrinolytic therapy Composite endpoint 30 day 13.7 8.0 18 (12 to 38)

Cardiology
CAD¹⁹ Perindopril vs placebo Large MI or death 4.2 years 9.9 8.0 54 (35 to 115)

Gastroenterology
H pylori infection²⁰ Clarithromycin. Iansoprazole, metronidazole vs clarithromycin, Iasoprazole, amoxicillin
Eradication of H pylori 6 weeks 84 66 6 (3 to infinity)

Infectious Disease
meningitis²¹ Dexamethasone vs placebo death 8 weeks 25 15 1 (5 to 73)

Nutrition
CAD²² Indo-Mediterranean diet vs control Prevention of CAD 2 years 15.2 7.8 14 (9 to 29)

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