Journal Club Summary
Methodology Score: 4/5
Usefulness Score: 4.5/5
Kline JA, et al. J Thromb Haemost. 2008 May;6(5):772-80.
In this prospective multicenter validation study, the PERC rule was found to have a sensitivity of 97.4% (CI 95.8-98.5%) and a negative likelihood ratio of 0.17 when applied to patients where physicians had determined that the pre-test probability of venous thromboembolism was low (<15%). Therefore, when a patient of low pre-test probability is found to be PERC negative, no further workup (including d-dimer) is needed to be able to say that and the chance that they will have a venous thromboembolic event in the next 45 days is less than 2%; although, JC attendees questioned whether the pre-test probability of a physician in American practice was equal to that of a physician seeing the same patient in Canadian practice.
By: Dr. Chris Fabian
(Presented June 2014)
Epi lesson: Why 2X2 Tables are Important
It is important for the critical reader that studies evaluating the properties of a diagnostic test present the 2X2 contingency tables (disease positive/negative at the top and test positive/negative on the left). This allows the reader to verify the sensitivity, specificity and also calculate positive and negative predictive values and likelihood ratios. Without the raw data of a 2X2 table, these key measures are not always obtainable.
By: Dr. Lisa Calder