Evidence base of clinical diagnosis

邓贝贝张棣王迎

Category of diagnostic test

• laboratory examination•medical history and information from physical

examination• imaging text like X-ray 、 MRI 、 CT etc.•accepted clinical diagnosis standards•ECG etc.

•Inflammatory breast cancer ：X-ray ？ CT ？ CEA？

•Unstable Angina: ECG? TnI? TnT?

Which test is the most appropriate for a certain condition？•We need to consider comprehensively——

evidence base of clinical diagnosis

•The key point of EBM is that clinical intervention or decision should be based on the current best evidence.

•It should be based on the current best evidence to decide which diagnosis test or which diagnosis standard to use for a patient .

Source of diagnosis evidence

•Literature of quality diagnosis test evaluation

•Literature of systematic review or meta-analysis

Evaluation of diagnosis test include:

•Validity evaluation of diagnosis test

•Reliability evaluation of diagnosis test

•Practicability evaluation of diagnosis test

sensitivity=a/a+c PPV=a/a+bspecificity=d/b+d NPV=d/c+dAgreement rate=a+d/a+b+c+dprevalence=a+c/a+b+c+d

Fourfold table

Validity evaluation

•Sensitivity;•False negative rate;•Specificity;•False positive rate;•Likelihood ratio;

Reliability evaluation

•Kappa value;

•Predictive value(PV): positive PV, negative PV;

ROC curve

0%

20%

40%

60%

80%

100%

0% 20% 40% 60% 80% 100%

false positive rate

True positive rate

(sensitivity)

•To determine the best critical point

•To compare the value of two or more diagnostic tests.

Function of ROC curve

Ways to improve the quality of diagnostic evidence

•Enough sample size•Reasonable statistical inference•Good control of bias•Reasonable normal reference value

Steps of evidence base of clinical diagnosis

•Propose clinical diagnosis question •Literature research•Literature evaluation•Summarize the information and apply it to

solve your question

Thank you