Critical Appraisal - diagnostic test. This calculator works off-line. (IE4)

Programme written by DJR Hutchon. Enter data into the boxes "A","B","C",and "D" VALIDITY CHECKS
Result of gold standard test
Disease positive Disease negative
(A+C) (B+D)
Result of diagnostic (or screening) test Test positive A+B= A (true pos)= B (false pos)=
Test negative C+D C (false neg)= D (true neg)=

Total (A+B+C+D) = Positive predictive value = 95% CI= Sensitivity = Pre-test probability (prevalence) =
Negative predictive value = 95% CI Specificity = Pre-test odds =
Post-test odds =
Liklihood ratio for positive test result = Liklihood ratio for negative test result =
Accuracy = Post-test probability =
from sensitivity, specificity, gold standard positive and total if raw data not provided. Calculator will also work if only true pos, true neg, gold standard pos, and total values are entered. APPRAISAL CRITERIA FOR A VALID TEST Return to calculator
Enter title and reference of paper appraised
For the result of the evaluation of a diagnostic test to be valid
1: There must be blind and independent comparison of the test with an established "gold" standard.
2: All the patients must be the appropriate group in which the test would be used in clinical practice. i.e. the test group were not selected.
3: The reference standard applied regardless of the diagnostic test result.

Enter data into the boxes "A", "B", "C", and "D" then click on the calculate button. Or you can enter the values of the true positives (A), the true negatives (D), the Gold standard positives (A+C) and the total (A+B+C+D) if only these results are available then click on the calculate button. A permanent record of the analysis can be obtained by printing the page.
Normogram for pre-test and post-test probability. Enter any two values (Third box must be blank)
Pre-test probability % Likilhood ratio Post-test probability %

This calculator is for educational use. It is believed accurate but no responsibility for accuracy of the results is accepted by the author. David J R Hutchon BSc, MB, ChB, FRCOG Consultant Gynaecologist, Memorial Hospital, Darlington, England.
References Newcombe RG. Stat Med 1998, 17, 857-872; 873-890; 2635-2650.
Wilson EB. J Am Stat Assoc 1927, 22, 209-212.
You are welcome to keep this page and use the calculator off-line. I would appreciate an E-mail if you find it useful enough to do so. E-mail to me at