1. EVIDENCE ABOUT DIAGNOSTIC TESTS Min H. Huang, PT, PhD, NCS

2. Diagnostic Tests Test threshold and treatment threshold  Help focus the exam in a particular body region or system.  Identify potential problems that require referral to other health care providers.  Assist in the diagnostic classification (i.e. a specific practice pattern).  Diagnostic tests MUST be reliable and valid.

3. Study Credibility  Appraisal of evidence begins with assessment of research validity.  Higher levels of validity indicate greater confidence that there is a lack of bias.  Lists of specific questions to ask (Table 10-1 in the textbook).

4. Specific Questions to ask  Can the research questions or hypotheses be tested with the research design  Did the investigators compare results from the diagnostic test to results from a “gold standard” diagnostic test  Were all subjects evaluated with the comparison diagnostic test  Were the individuals performing and interpreting each test’s result unaware of the other test’s results (i.e. were they masked, or blinded)

5. Specific Questions to ask  Did the investigators include subjects with all levels of stages of the condition being evaluated by the measure of interest  Did the investigators confirm their findings with a new set of subjects  Did the study use appropriate statistical analysis methods for reliability and validity  Correlation coefficients  Face, construct, criterion, concurrent validity  Were p values or C.I. significant?

6. Study Results  Sensitivity (SnNout)  Specificity (SpPin)  Positive predictive value (PPV)  Negative predictive value (NPV)  Likelihood ratios (LR):  reflect a diagnostic test’s ability to provide persuasive information  LR + = Sn/(1-Sp)  LR – = (1-Sn)/Sp  Receiver Operating Characteristic Curves (ROC)  a graphic way to evaluate different thresholds of a test

7. Loong et al. (2003).

8. Sn = 24/30 = 80%

9. Sp = 56/70 = 80%

10. PPV = 24/38 = 63%

11. NPP = 56/62 = 90%

12. Figure 10-7: A Receiver Operating Characteristic (ROC) Curve for an Imperfect but Useful Test

13. Likelihood Ratio Nomogram  Use a nomogram to calculate posttest probability, i.e. the probability that the patient/client has the condition after a test result is obtained.  LR+ = 1-2, LR- = 0.5-1.0  negligible change in pretest probability http://www.cebm.net/index.aspx?o=1043

14. EVIDENCE ABOUT CLINICAL MEASURES Min H. Huang, PT, PhD, NCS

15. Clinical Measures  Are NOT used to label or classify a diagnosis or practice pattern  Quantify and/or describe a patient’s impairments in a standardized fashion  Distinguish among different levels of severity of a problem  Instruments must have reliability, validity, responsiveness

16. Study Credibility  SAME process as diagnostic tests  Refer to questions in Table 10-2  Clinical measures MUST be validated in patient populations with different diagnoses

17. Study Results  Reliability and validity are confirmed by correlation coefficients.  Responsiveness is commonly assessed by  Minimal detectable change (MDC): the amount of change that just exceeds the standard error of measurement  Standardized response mean (SRM): the ratio between the mean change score and the standard deviation of the change scores; reflect the change over time

18. Considerations for Implementing the Evidence into Practice  Test or measure should be available, practical and safe in the setting  Test or measure should have demonstrated performance on similar patient/clients  Can pretest probabilities be estimated for the patient/client  Patient/client’s preferences and values

19. Review  Most useful diagnostic tests and clinical measures have demonstrated reliability and validity  Reliability is shown through statistical tests of relationships among repeated test results  Validity is demonstrated through statistical tests or comparison to the gold standard  Responsiveness is measured MDC or SRM

20. IMPACT OF PAIN REPORTED DURING ISOMETRIC QUADRICEPS MUSCLE STRENGTH TESTING IN PEOPLE WITH KNEE PAIN: IMPACT OF PAIN REPORTED DURING ISOMETRIC QUADRICEPS MUSCLE STRENGTH TESTING IN PEOPLE WITH KNEE PAIN: DATA FROM THE OSTEOARTHRITIS INITIATIVE DANIEL L. RIDDLE, PAUL W. STRATFORD Min H. Huang, PT, PhD, NCS

21. Introduction  Common clinical assumption  Impairments in body structure or function (e.g. pain) can impact limitations in activities and participation (e.g. physical function)  Limitations of previous research  NO large scale studies available  Does pain affect muscle strength? 1 study: Yes 1 study: No

22. Relationships between Domains of the ICF Model

23. Purpose  Whether the relationship between maximal isometric quad strength (X1) and functional status (Y1,Y2,….Y5) was influenced by pain during isometric testing (X2)  The extent to which pain during testing (X1) affected quad strength (Y1), or other functional tests (Y2, Y3, Y4, Y5)

24. Purpose Model 1 (Initial): Physical Function (Y) = β1 Strength (X1) + covariates + ε Model 2 (Full): Physical Function (Y) = β1 Strength (X1) + β2 Pain (X2) + β3 Strength (X1) × Pain(X2) + covariates + ε Y X Y X

25. Purpose Model 3 (No interaction) Physical Function (Y) = β1 Strength (X1) + β2 Pain (X2) + covariates + ε Y X Y X Model 1 Y X Model 2

26. Purpose – Class Discussion

27. Method  Participants (n=1,344)  Unilateral knee pain Verbal Numerical Rating (VNR) > 3  WOMAC pain >1  Outcome variables  WOMAC physical function  20-m walk  400-m walk  5 times sit to stand  Independent variables  MAX Quad strength  Pain during Quad strength testing  Multiple regression models  Model 1  Model 2  Model 3  95% CI of β excludes 0

28. Method – Class Discussion

29. Results Pain did NOT modify or confound any of the outcome variables: 400-m walk, 20-m walk, chair stand, WOMAC – Physical Function.

30. Results Table 6. MODERATE or SEVER pain during testing was WEAKLY associated with reduced STRENTGH, but mild pain was not.

31. Results – Class Discussion

32. Discussion  Pain during maximal isometric Quad strength tests did not affect the construct validity of the tests  Isometric Quad muscle strength and functional status relationship is NOT affected by reports of pain during testing

33. Discussion – Class Discussion

34. Limitations  Were the samples representative of the population treated?  Measurement of pain? No psychometric properties reported.  Muscle strength measured by dynamometer – Is it applicable to clinical settings using MMT?  No Hypotheses; No power estimate – finishing expedition?