Manual muscle testing: does it meet the standards of an adequate screening test?

OBJECTIVE: To describe the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of manual muscle testing. DESIGN: Secondary analysis of cross-sectional strength data. SETTING: Acute rehabilitation unit. PARTICIPANTS: Convenience sample of 107 consecutive qualifying rehabilitation inpatients. INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Knee extension forces measured by manual muscle testing and hand-held dynamometry. RESULTS: The ability of manual muscle testing to detect 15, 20, 25 and 30% between-side differences and deficits in knee extension force was described. Although the specificity of manual muscle testing was acceptable (mostly > 80%), its sensitivity to differences between sides and to deficits relative to normal never exceeded 75%. Its diagnostic accuracy was never greater than 78%. CONCLUSION: The results of this study cast doubt on the suitability of manual muscle testing as a screening test for strength impairments.