More Details on Likelihood Ratios
DefinitionThe 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.
How to Calculate LRsWe can assume that there are four possible groups of patients, as indicated (a,b,c,d) in the table below:
|Diagnostic Test Result||+||
a + b
c + d
|Totals||a + c
||b + d
From these we can determine the sensitivity and specificity as follows:
Sensitivity = a/(a+c)
Specificity = d/(b+d)
We can now use these to calculate the likelihood ratio for a positive test result (LR+):
LR+ = sensitivity/(1-specificity)
Similarly, we can calculate the likelihood ratio for a negative test result (LR-):
LR- = (1-sensitivity)/specificity
Sample CalculationSuppose you have a patient with anemia and a serum ferritin of 60 mmol/L. You come across a systematic review (J Gen Intern 1992; 7:145-53) of serum ferritin as a diagnostic test for iron deficiency anemia, with the results summarised as follows in the table:
(iron deficiency anemia)
|Diagnostic Test Result
a + b
c + d
|Totals||a + c
|b + d
These results indicate that 90% of the patients with iron deficiency anemia have a positive test result
(serum ferritin < 65 mmol/L). This is known as the sensitivity and is calculated as:
Sensitivity = a/(a+c) = 731/809 = 90%
The results also show that 85% of patients who do not have iron deficiency anemia have a negative test result. This is referred to as the specificity, calculated as:
Specificity = d/(b+d) = 1500/1770 = 85%
From these the positive and negative likelihood ratios can be determined:
LR+ = sensitivity/(1-specificity) = 90%/15% = 6 LR- = (1-sensitivity)/specificity = 10%/85% = 0.12
Thus, from your calculation of LR+ you determine that your patient's positive test result would be about 6 times as likely to be seen in someone with iron deficiency anemia than in someone without the disorder.
Practice CalculationThe results of a blinded study (Stroke 1996;27:1516-20) assessing the use of plasma D-dimer levels for diagnosing deep venous thrombosis (DVT) in patients hospitalised for stroke rehabilitation are summarised in the table below. The presence or absence of DVT was determined by positive or negative venous duplex ultrasound results.
|Diagnostic Test Result
(Plasma D-dimer level)
a + b
c + d
|Totals||a + c
|b + d
What would the likelihood ratio for a positive test result (LR+) and the likelihood ratio for a negative test result (LR-) be?
LR+ = _______
LR- = _______
See our answer and compare
Sensitivity = a/(a+c) = 13/14 = 93%
Specificity = d/(b+d) = 72/91 = 79%
LR+ = sensitivity/(1-specificity) = 93%/21% = 4.4
How to Use LRs
The likelihood ratio is used to assess the value of a diagnostic test, sign or symptom. High likelihood ratios (e.g., LR>10) indicate that the test, sign or symptom can be used to rule in the disease, while low likelihood ratios (e.g., LR < 0.1) can rule out the disease. Likelihood ratios of around 1 indicate that no useful information for ruling the diagnosis in or out has been produced from the clinical findings.
Likelihood ratios can also be used to calculate the post-test probability for a disorder, which is another way to assess the value of a diagnostic test. For example, suppose you have a patient with anemia and prior to doing the serum ferritin test you think the chance that she has iron deficiency anemia is 50-50. Thus, her pre-test probability is 50%, which is equivalent to a pre-test odds of 1:1. You also determine that the likelihood ratio for a positive serum ferritin test result is 6 (see Sample Calculation above). The post-test probability can now be calculated as follows:
post-test odds = 1 x 6 = 6
post-test probability = 6/(6+1) = 86%
The serum ferritin test is performed and your patient is found to have a serum ferritin concentration of 60 mmol/L. The increase in probability from 50% (pre-test) to 86% (post-test), suggests that the serum ferritin test is useful for determining whether or not your patient has iron deficiency anemia.
Criteria for Inclusion of Examples(Modified from criteria used by ACP Journal Club)
- Inclusion of an appropriate spectrum of patients - both those with and without the target disorder of interest.
- Interpretation of diagnostic standard without knowledge of the test result.
Interpretation of the test without knowledge of the diagnostic standard result.
Each person must receive the new test and the diagnostic standard use of an objective criterion standard measure of diagnosis or current clinical standard for diagnosis.
Tables of Examples
|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|
|Alzheimers 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|
|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) 8||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|
|DVT9||Homan's sign (positive if no dorsiflexion of the foot on squeezing the calf muscles)||Hospital patients||1.5||0.6|
|Adult meningitis10||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)11||Abdominal palpation; AAA ≥ 3.0cm||Ultrasound||Systematic review; 15 studies of patients not previously known to have AAA||12.0
|Same as above||Same as above||15.6
|Ascites12||Fluid wave||Abdominal ultrasound||Inpatients veteran with evidence of liver disease examined by internists||9.6||0.2|
|Postnatal depression13||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)14||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)15||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)16||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 people17||15 item Geriatric Depression Scale (GDS)||Schedules for Clinical Assessment in Neuropsychiatry to make ICD-10 (criteria for mood disorders) diagnoses||Patients were ≥75 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 patients18||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 ≥65 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 patients19||D-dimer analysis||All DVT||Patients with suspected DVT at a university hospital in Switzerland||2.0||0.3|
|Predicting ectopic pregnancy20||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|
|Helicobacter pylori infection21||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 DVT22||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 23||Virtual colonoscopy||Conventional colonoscopy done using a standard endoscope||Adults aged 50 to 77 years of age at a high risk of colorectal neoplasia (≥ 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 ≥ 1 first-degree relatives)||5.0||0.2|
|Urinary tract infection in children24||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 infection25||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 children26||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≥1 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 ≥ 6 days||3.4||0.1|
|Clinical judgment||All children||1.7||0.5|
|Hypoxia in infants27||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 ≥ 40 breaths/min||2.2||0.4|
|≥ 50 breaths/min||2.2||0.2|
|≥ 60 breaths/min||2.5||0.3|
|≥ 70 breaths/min||3.3||0.6|
|≥ 80 breaths/min||3.4||0.8|
|Polyneuro-pathy in type 2 diabetes mellitus28||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|
|≥ 68 years of age||2.75||0.85|
|Pathologic findings in the common bile duct (CBD)29||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
|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 jaundice30||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 dysfunction31||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 adults32||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 ≥45 years: 1.3||Age ≥45 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)33||Abdominal palpations||Ultrasonograpgy||Patients were between the ages of 51 and 88 and had known AAAs (≥3cm 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 ≥100cm: 3.2||Girth ≥100cm: 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 ≥100cm and aorta palpable: 2.0||Girth ≥100cm and aorta palpable: 0.30|
|Psychiatric disorders34||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 dependence35||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 months and had a stable maintenance dose of their benzodiazepine equivalent to 5-50 mg/day of diazepam||17||0.02|
|Urinary tract infection36||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 people37||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 infants38||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:
|Lower limit for SpO2:
|Detecting hyperoxia in sick infants39||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:
|Upper limit for SpO2:
|Mild dementia in older persons40||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)41||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|
|Dementia42,43||Clock drawing test||NINCDS-ADRDA criteria||Elderly patients||9.6||0.4|
|Cirrhosis44||Encephalopthy||Needle biopsy of liver||Patients with severe chronic active liver disease||17.5||0.7|
|Anemia45||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|
|Hypovolemia46||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 fever47||Patients' report of fever||Measured temperature >38? C||Ambulatory adult patients in a military tertiary care emergency department||4.9||0.2|
|Pulmonary embolism48,49||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 Failure50,51,52,53,54||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|
|Cardiomegaly55||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|
|Stenosis56,57||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 Sound58,59||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 Murmurs60,61||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 Stenosis62,63||Arterial pulse-reduced carotid artery volume||Aortic valve area < 0.75cm, < 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 Enlargement64,65,66||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|
|Ascites67,68,69||Inspection-bulging flanks||Peritoneal fluid by ultrasonography||Patients suspected of having ascites||1.9||0.4|
|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 Syndrome70||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|
|PMNs in Ascitic Fluid||Spontaneous Bacterial Peritonitis71 (based on reference standard)||LR (Likelihood Ratio)|
|Present (n%)||Absent (n%)|
Note regarding DVT
|Target Disorder||Clinical Features
(History and examination can help decide about further tests, but cannot rule out DVT)
|Deep venous thrombosis (DVT)||Active cancer (on-going treatment, or diagnosed within 6/12 or palliative care)||1|
|Paresis, paralysis or recent plaster-cast immobilisation of lower extremity||1|
|Recently bed-ridden>3 days &/or major surgery< 4/52||1|
|Localised tenderness over distribution of deep veins||1|
|Entire leg swollen||1|
|Calf swelling 3cm>symptomless side, measured at 10cm below tibial tubercle||1|
|Pitting oedema symptomatic leg only||1|
|Collateral superficial veins (non-varicose)||1|
|Alternative diagnosis as likely or greater than that of DVT||-2|
The resulting score places the patient into one of three risk groups:
|0 or less||low||0.16|
|1 or 2||moderate||1.0|
|3 or more||high||16|
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