Definition
The Likelihood Ratio (LR) is the likelihood that a given test result would be expected in a patient with the target disorder compared to the likelihood that that same result would be expected in a patient without the target disorder.

*(J Gen Intern 1992; 7:145-53)

^*(Stroke 1996;27:1516-20)

Instead of doing these calculations, we could obtain the same result much more quickly using the stats calculator.

TARGET DISORDER	SIGN, TEST, SYMPTOM	REFERENCE STANDARD	PATIENT, POPULATION, SETTING	LR+ (95% CI)
Dementia1	Mini-Mental Status Examination (MMSE) score at the 26/27 cut-off point	Diagnosis of dementia and depression made by senior psychiatrists using a checklist of DSM-III-R criteria	Patients admitted to a university geriatric hospital or outpatient memory clinic in Switzerland	2.5
Deep Venous Thrombosis (DVT)2	Plasma D-dimer level > 1092 ng/mL	Venous duplex ultrasonography (VDU)	Patients hospitalised in a stroke rehabilitation unit in the US	3.1
Group A b-haemolytic streptococcus (GABHS) pharyngitis3	Positive rapid streptococcal antigen detection test	Throat culture	Patients with sore throat presenting to general practices in the Netherlands	15.2
Proximal DVT4	Ultrasonography	Venography	Symptomatic patients	47.5
DVT4	Ultrasonography	Venography	Asymptomatic patients	7.8
Alzheimer's Disease (AD)5	Positive apolipoprotein E (APOE) genotype test	Criteria from the National Institute of Neurological Disorders & stroke or the DSM-III-R	Patients referred for evaluation of dementia in AD centres in US	2.0
Peripheral vascular disease6	Unilateral cool limb	Ankle-to-arm systolic pressure index	Systematic review of 17 studies	5.8
Arterial stenosis6	Limb bruit	Ankle-to-arm systolic pressure index	Systematic review of 17 studies	3.2
Myocardial Infarction (MI)7	Any ST-segment elevation on an ECG	Diagnosis of MI based on World Health Organization (WHO) criteria = confirmation by ECG and lab test results	Adult patients with chest pain	11.2
Myocardial Infarction7	Radiation of pain to both arms	Diagnosis of MI based on WHO criteria	Adult patients with chest pain	7.1
Myocardial Infarction7	New conduction defect	Diagnosis of MI based on WHO criteria	Adult patients with chest pain	6.3

Target Disorder	Sign, Test, Symptom	Reference Standard	Patient, Population, Setting	LR+ 95% CI	LR- 95% CI
Deep venous thrombosis (DVT)1	Compression ultrasound (USS) in all patients	Venography	Hospital patients	39	0.23
	USS in high risk	Venography	Hospital patients	∞	0.09
	USS in moderate risk	Venography	Hospital patients	53	0.39
	USS in low risk	Venography	Hospital patients	24	0.34
DVT2	Homan's sign (positive if no dorsiflexion of the foot on squeezing the calf muscles)		Hospital patients	1.5	0.6
Adult meningitis3	Jolt accentuation of headache	Lumbar puncture or autopsy	Patients presenting to outpatient or emerg. dept. with headache and fever; n=30, all with objectively confirmed meningitis	2.2	0
Abdominal aortic aneurysm (AAA)4	Abdominal palpation; AAA ³ 3.0cm	Ultrasound	Systematic review; 15 studies of patients not previously known to have AAA	12.0 (7.4-19.5)	0.72 (0.65-0.81)
AAA4	Abdominal palpation; AAA ³ 4.0cm	Same as above	Same as above	15.6 (8.6-28.5)	0.51 (0.38-0.67)
Ascites5	Fluid wave	Abdominal ultrasound	Inpatients veteran with evidence of liver disease examined by internists	9.6	0.2
Postnatal depression6	Number of routine and non-routine contacts had by general practitioners (GPs), health visitors (HVs), midwives (Ms) and whole primary healthcare teams (WPHTs) with mothers 42 days after delivery and whether or not they were aware of postnatal depression in the mother. Sensitivity and specificity for detecting postnatal depression were also measured.	The Edinburgh Postnatal Depression Scale (EPDS) score > 11	Mothers who attended their postnatal examination at 6-8 weeks after delivery. Set in 7 general practices in Bolton, UK.	GPs: 8.06	GPs: 0.70
				HVs: 3.04	HVs: 0.86
				Ms: 12.42	Ms: 0.80
				WPHTs: 5.27	WPHTs: 0.62
Myocardial Infarction (MI)7	Cardiac-specific troponin T (cTnT) was measured using a handheld device containing specific monoclonal antibodies and was read by a clinical chemistry technologist blinded to the other test results at two different times.	Clinical evaluation, ECG readings, CK and CK-MB quantitative assays or autopsy results by a blinded observer	Patients presenting to the hospital with chest pain suggestive of MI. Set in a coronary care and telemetry unit of a tertiary care university medical center	At 0-2 hours: 6.3	At 0-2 hours: 0.8
				At >8 hours: 6.0	At >8 hours: 0.15
Deep venous thrombosis (DVT)8	D-dimer analysis alone	Duplex ultrasound scanning	Patients with suspected DVT. Set in a university hospital in Basel, Switzerland.	2.0	0.3
	D-dimer analysis plus clinical assessment			1.8	0.09
Abdominal aortic aneurysm (AAA)9	Abdominal palpation during physical examination	Ultrasound	Half of the patients had AAA, half did not (determined by previous ultrasound)	2.7	0.43
Depression in elderly people10	15 item Geriatric Depression Scale (GDS)	Schedules for Clinical Assessment in Neuropsychiatry to make ICD-10 (criteria for mood disorders) diagnoses	Patients were ³75 years of age, were not in residential care and had completed the diagnostic interview after completing the GDS 15. Set in a large general practice in Leicestershire, UK	Depression 4.3	Depression 0.2
				Anxiety 3.4	Anxiety 0.4
Depression in elderly patients11	Even Briefer Assessment Scale for Depression (8 questions on depressive mood, worries, suicidal thoughts and vegetative symptoms)	Diagnoses made by a psychiatrist or psychiatric nurse who used the Feighner criteria	Patients were ³65 years of age. Set in an old age home, a day clinic and a psychiatric hospital in Germany	6.2	0.8
Deep Venous Thrombosis (DVT) in symptomatic patients12	D-dimer analysis	All DVT	Patients with suspected DVT at a university hospital in Switzerland	2.0	0.3
Predicting ectopic pregnancy13	Clinical prediction guide: High risk women had signs of peritoneal irritation or definite cervical motion tenderness. Intermediate risk women had no fetal heart tones by handheld Doppler, no tissue visible at the cervical os and pain or tenderness	High risk	Women who were haemodynamically stable and had abdominal pain or vaginal bleeding in the first trimester of pregnancy	6.1	0.7
		Intermediate risk		1.4	0.0
Helicobacter pylori infection 14	13C-Urea blood test (13C-UBT - patients received 125 mg dissolved in 75 ml of water)	Positive test for histologic testing	Patients (mean age 49 y, 51% men) who were referred for endoscopy at 5 medical centers in the United States	19.9	0.1
	Rapid urease testing (RUT)			19.4	0.1
	13C-UBT	Positive test for histologic testing and positive RUT		10.4	0.1
	13C-UBT	Positive test for histologic testing or positive RUT		44.0	0.1
Symptomatic DVT15	D-dimer levels were assessed using a rapid whole blood assay (SimpliRed)	Duplex ultrasono-graphy scanning (DUS)	High risk for DVT based on clinical assessment score that included data on the presence of cancer, immobilization, localized tenderness, history of leg trauma, unilateral edema or erythema, dilated superficial veins and hospitalization	1.9	0.0
			Patients at moderate risk for DVT	3.4	0.3
			Patients at low risk for DVT	7.5	0.3
Colorectal polyps and cancer 16	Virtual colonoscopy	Conventional colonoscopy done using a standard endoscope	Adults aged 50 to 77 years of age at a high risk of colorectal neoplasia (³ 50 y of age, with a history of adenomatous polyps, recent sigmoidoscopic evidence of ³ 1 polyp, a positive finding on fecal occult-blood testing or a history of colorectal cancer in ³ 1 first-degree relatives)	5.0	0.2
Urinary tract infection in children17	Uriscreen test	Quantitative urine culture, done using the commercial Diaslide method	Random sample of 121 children (1 month to 17 years of age) who presented at the emergency department with symptoms of UTI at a children?s hospital in Israel.	3.2	∞
	Dipstick test (Multistix 10 SG strip)			5.6	0.03
	Urinalysis done in the hospital laboratories with an automated urine analyzer			7.6	0.13
Helicobacter pylori infection18	Near-patient test (FlexSure) testing serum from a clotted sample	Enzyme-linked immuno-sorbent assay (ELISA)	Patients aged from 18 to 73 years of age and had symptoms of dyspepsia of sufficient severity to justify empiric treatment with H2-antagonists or proton-pump inhibitors.	32.4	0.3
Pneumonia in children19	Tachypnea (defined as a respiratory rate > 60 breaths per minute in children < 2 months of age, > 50 breaths per minute in children 2 to 12 months of age and > 40 breaths per minute in children ³1 year of age)	Chest Radiography	110 children who were 3 days to 5 years of age and had acute respiratory infection	2.2	0.4
			Children with disease duration < 3 days	1.5	0.7
			Children with disease duration 3 to 5 days	1.9	0.5
			Children with disease duration ³ 6 days	3.4	0.1
	Clinical judgment		All children	1.7	0.5
Hypoxia in infants20	Respiratory rate was counted for 1 minute while observing the infants chest and abdominal movements when the infant was quiet.	Assessment of oxygen saturation (measured at the finger or toe with a pulse oximeter). Hypoxia was defined as an oxygen saturation level £ 90%	Infants who were < 2 months of age and had symptoms of any acute illness and whose respiratory rate was ³ 40 breaths/min	2.2	0.4
			³ 50 breaths/min	2.2	0.2
			³ 60 breaths/min	2.5	0.3
			³ 70 breaths/min	3.3	0.6
			³ 80 breaths/min	3.4	0.8
Polyneuro-pathy in type 2 diabetes mellitus21	Patients completed a 34-item diabetes symptom checklist that measured the physical and psychological symptoms related to type 2 diabetes	Clinical neurologic examination done by a trained research clinician who was blinded to the results of the checklist	Patients with type 2 diabetes mellitus who received care in general practice who were < 68 years of age	4.0	0.77
			³ 68 years of age	2.75	0.85
Pathologic findings in the common bile duct (CBD)22	Abnormal findings on biliary scintigraphy	Endoscopic or preoperative cholangio-graphy	75 consecutive patients with symptomatic gallstone disease at a tertiary referral center in Bombay, India	15	0.07
	Pathologic findings in the common bile duct (CBD) Abnormal findings on biliary scintigraphy CBD > 9mm with ultrasonography			∞	0.4
	CBD stone with ultrasonography			∞	0.5
	Abnormal bile duct with ultrasonography			17	0.3
	All standard criteria combined			1.7	0.23
	Modified standard criteria			3	0.2
	Ultrasonography and scintiscan			78	0.04
Neonatal jaundice23	Clinical examination – infants were observed by 2 clinicians under fluorescent lighting near a window. Clinicians assessed jaundice as being absent, slight or obvious for prespecified body zones	Serum bilirubin test	122 healthy full-term infants (mean age 2 days, 54% boys)	1.9	0.15
Assessing left ventricular systolic dysfunction24	Physical examination, chest radiography, echocardiography, supine 12-lead electrocardio-graphy, blood pressure measurements and blood tests	Left ventricular systolic dysfunction was defined as an ejection fraction of < 0.45 and was determined from videotapes and photoecho-cardiograms by an investigator blinded to the other clinical data	Patients with abnormal electrocardio-graphic results	1.96	0.24
			Patients with N-terminal atrial natriuretic peptide level > 0.8 nmol/L	3.82	0.62
			Patients with heart rate > diastolic pressure	3.91	0.55
Chronic obstructive airway disease (COAD) in adults25	Spirometry was done within 30 minutes of clinical examination with the better attempt of 2 efforts recorded	COAD confirmed if FEV1 and FEV1:FVC ratio were < 5th percentile	Patients were recruited so that approximately one-third had confirmed OAD, one-third had suspected OAD and one-third had no evidence of OAD	Self reported history of OAD: 7.3	Self reported history of OAD: 0.5
				Smoking >40 pack per year: 8.3	Smoking >40 pack per year: 0.8
				Age ³45 years: 1.3	Age ³45 years: 0.4
				Maximum laryngeal height £ 4cm: 2.8	Maximum laryngeal height £ 4cm: 0.8
				All factors present: 221	All factors present: 0.13
Abdominal aortic aneurysm (AAA)26	Abdominal palpations	Ultrasonograpgy	Patients were between the ages of 51 and 88 and had known AAAs (³3cm in diameter) or had known absence of AAAs	All examinations: 2.7	All examinations: 0.43
				Girth <100cm: 2.5	Girth <100cm: 0.14
				Girth ³100cm: 3.2	Girth ³100cm: 0.56
				Abdomen not obese: 2.6	Abdomen not obese: 0.17
				Abdomen obese: 2.9	Abdomen obese: 0.64
				Abdomen not tight: 2.3	Abdomen not tight: 0.38
				Abdomen tight: 4.7	Abdomen tight: 0.54
				Aorta palpable: 2.0	Aorta palpable: 0.22
				Girth ³100cm and aorta palpable: 2.0	Girth ³100cm and aorta palpable: 0.30
Psychiatric disorders27	Quick PsychoDiagnostics Panel (automated test that patients complete by answering true/false questions)	Structured Clinical Interview for DSM-IV diagnoses	HMO patients referred by their physicians or self-referred for a first time mental health consultation and were not receiving mental health treatment at study entry	Major depression: 20.3	Major depression: 0.2
				Generalised anxiety disorder: 7.9	Generalised anxiety disorder: 0.2
				Panic disorder: 23.7	Panic disorder: 0.3
				Obsessive compulsive disorder: 23.0	Obsessive compulsive disorder: 0.3
Benzodiazepine dependence28	Severity of Dependence Scale	Composite International Diagnostic Interview	Participants were 18-75 years of age (75% women), had neurotic diagnosis, continuously used benzodiazepine daily for ³ 3 months and had a stable maintenance dose of their benzodiazepine equivalent to 5-50 mg/day of diazepam	17	0.02
Urinary tract infection29	Visual inspection of urine samples	Laboratory urinalysis including dipstick testing for presence of nitrites and leukocyte esterase, bacteria on microscopy and white cell count	Healthy patients < 21 years of age (77% girls) who had either a catheterised or midstream urine specimen collected for urine culture at an emergency department of a children's hospital in Cincinnati, Ohio, USA	All specimens: 5.07	All specimens: 0.13
				Cathetrised specimens: 6.04	Cathetrised specimens: 0.19
				Midstream specimens: 4.52	Midstream specimens: 0.07
Mild dementia in older people30	Hopkins Verbal Learning Test	DSM-IV criteria	56 patients (mean age 75 years, 63% women, mean education 8.5 years)	4.80	0.05
	Mini-Mental State Examination	DSM-IV criteria		12.75	0.13
Detecting hypoxia in sick infants31	Measurements of SpO2 and partial pressure of oxygen in arterial blood in order (PaO2 <6 kPa indicated hypoxemia)	Partial pressure of oxygen in arterial blood (PaO2)	Infants who required arterial lines at a neonatal intensive care unit in Liverpool, UK	Lower limit for SpO2: 88%: 1.43 89%:1.24 90%: 1.57 91%: 1.64 92%: 1.57 93%: 1.38 94%: 1.33 Individualised*: 1.26	Lower limit for SpO2: 88%: 0.87 89%:0.88 90%: 0.69 91%: 0.50 92%: 0.419 3%: 0.41 94%: 0.33 Individualised*: 0.69
Detecting hyperoxia in sick infants32	Measurements of SpO2 and partial pressure of oxygen in arterial blood in order (PaO2 >10 kPa indicated hyperoxemia)	Partial pressure of oxygen in arterial blood (PaO2)	Infants who required arterial lines at a neonatal intensive care unit in Liverpool, UK	Upper limit for SpO2: 94%:1.37 95%: 1.67 96%: 1.95 97%: 5.25 98%: 0.79 Individualised*: 2.08	Upper limit for SpO2: 94%: 0 95%: 0 96%: 0.34 97%: 0.63 98%: 1.03 Individualised*: 0.39
Mild dementia in older persons33	The Hopkins Verbal Learning Test	DSM-IV criteria	56 patients (mean age 75 y, 63% women) participated at a geriatric psychiatric hospital in Australia	4.80	0.05
	Mini-Mental State Examination			12.57	0.13
Acute pulmonary embolism (PE)34	Dual-section helical computed tomography done in a caudocranial direction	Pulmonary digital subtraction arteriography	Patients were 18 to 75 years of age and had clinically suspected acute PE at a hospital radiology department in Boulogne, France	29.1	0.05
Dementia35,36	Clock drawing test	NINCDS-ADRDA criteria	Elderly patients	9.6	0.4
Cirrhosis37	Encephalopthy	Needle biopsy of liver	Patients with severe chronic active liver disease	17.5	0.7
Anemia38	Facial pallor	Hematocrit <35%, hemoglobin <11g/dl, or hemoglobin <11 g/dl in women and <13g/dl in men	Patients were selected so that there was equal representation in five hematocrit categories	3.8	0.6
	Nail bed pallor			1.7	0.6
	Palmar pallor			2.5	0.5
Hypovolemia39	Dry axilla	Elevated serum urea nitrogen-creatinine ratio, osmolarity, or sodium level	Patients were above the age of 70and were consecutively admitted with acute medical conditions	2.8	Not significant
Detection of fever40	Patients' report of fever	Measured temperature >38° C	Ambulatory adult patients in a military tertiary care emergency department	4.9	0.2
Pulmonary embolism41,42	Risk factors - known cancer	Positive pulmonary angiogram	Patients suspected of having a pulmonary embolism	4.1	0.8
	Heart rate >90/min			1.8	0.3
	Respiratory rate >20/min			1.7	0.5
	Calf pain or swelling			2.6	0.6
Congestive Heart Failure43,44,45,46,47	Elevated Venous Pressure at the bedside - Detecting central venous pressure (CVP) > 8 cm H2O	Measurement by catheter in supine position using method of Lewis	Patients having cardiac catheterization were studied	9.0	Not significant
	Elevated Venous Pressure at the bedside - Detecting (CVP) > 12 cm H2O			10.4	0.1
	Positive abdominojugular test - detecting elevated left heart diastolic pressures	Pulmonary capillary wedge pressure >15 mm Hg or left ventricular end diastolic pressure >15 mm Hg		8.0	0.3
Cardiomegaly48	Dullness extends more than 10.5 cm from midsternal line, patient supine - detecting cardiothoracic ratio >0.5	Maximal transverse diameter of heart on chest radiography divided by maximal transverse diameter of thoracic cage	Patients had a posteroanterior radiograph of the chest	2.5	0.05
Stenosis49,50	Hyperkinetic apical movement - detecting associated mitral regurgitation or aortic valve disease in patients with mitral stenosis	Aortic valve area < 0.75 cm, <0.8 cm, <0.9 cm; peak gradient >50 mm Hg; or peak gradient velocity of aortic flow >3.6 m/sec	Patients with cardiovascular problems	11.2	0.3
	Sustained apical movement - detecting severe aortic stenosis in patients with aortic flow murmurs			4.1	0.3
Third Hear Sound51,52	Detecting ejection fraction less than 0.3	Radionucleotide left ventricular ejection fraction <0.3	Patients with suspected or proved coronary heart disease who underwent radionucleotide angiography or ventriculography	4.1	0.3
Systolic Murmurs53,54	Changing venous return - louder with Valsalva strain - detecting hypertrophic cardiomyopathy	Doppler echocardiography or angiography	Patients with systolic murmur of Grade I/VI or higher	14.0	0.3
	Changing venous return - louder with squatting-to-standing - detecting hypertrophic cardiomyopathy			6.0	0.1
	Changing venous return - softer with passive leg elevation - detecting hypertrophic cardiomyopathy			9.0	0.1
	Changing systematic vascular resistance (afterload) - softer with isometric hand grip-detecting hypertrophic cardiomyopathy			3.6	0.1
	Changing systematic vascular resistance (afterload) - louder with isometric hand grip - Detecting mitral regurgitation or ventricular septa defect			5.8	0.3
	Changing systematic vascular resistance (afterload) - louder with transient arterial occlusion - Detecting mitral regurgitation or ventricular septa defect			48.7	0.2
Severe Aortic Stenosis55,56	Arterial pulse - reduced carotid artery volume	Aortic valve area < 0.75 cm, <0.8 cm, <0.9 cm; peak gradient >50 mm Hg; or peak gradient velocity of aortic flow >3.6 m/sec	Patients with suspected aortic stenosis	2.3	0.3
	Apical impulse - sustained apical impulse			4.1	0.3
Splenic Enlargement57,58,59	Splenic percussion signs - detecting enlarged spleen - Spleen percussion sign (Castell's)	Spleen enlarged by ultrasonography, scintigraphy or postmortem weight >200g or >250g	Patients who underwent splenic ultrasonography or scintigraphy	1.9	0.7
Ascites60,61,62	Inspection - bulging flanks	Peritoneal fluid by ultrasonography	Patients suspected of having ascites	1.9	0.4
	Inspection - edema			3.8	0.2
	Palpation and percussion - flank dullness			Not significant	0.3
	Palpation and percussion - shifting dullness			2.3	0.4
	Palpation and percussion - fluid wave			5.0	0.5
Carpal Tunnel Syndrome63	Hand diagram - "classic" or "probable"	Abnormal motor or sensory conduction within the carpal tunnel, measured by nerve conduction testing	Patients presenting with upper extremity discomfort were evaluated	2.4	0.5
	Hand diagram - "unlikely"			0.2	---

PMNs in Ascitic Fluid	Spontaneous Bacterial Peritonitis1 (based on reference standard)		LR (Likelihood Ratio)
	Present (n%)	Absent (n%)
>1000	33 g(g/ a+c+e+g)	10 h(h/ b+d+f+h)	22.3
501 - 1000	2 e(e/ a+c+e+g)	5 f(f/ b+d+f+h)	2.78
251 - 500	2 c(c/ a+c+e+g)	12 d(d/ b+d+f+h)	1.14
0 - 250	3 a(a/ a+c+e+g)	245 b(b/ b+d+f+h)	0.08
Totals	40 a+c+e+g (100%)	272 b+d+f+h (100%)

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