Objective: To use self-reported disability (Roland-Morris Disability Questionnaire [RMDQ]) to assess the criterion validity of straight leg raising (SLR) test and flexion range of motion (ROM) (fingertip-to-floor test) before and after stratification by sex and presence/absence of radicular pain.
Design: Cross-sectional study.
Setting: Outpatient physical therapy clinic.
Participants: Subjects with acute/subacute low back pain with (n=40) and without (n=35) radicular pain.
Interventions: Not applicable.
Main outcome measures: We examined the relationship between RMDQ (reference variable) and SLR test and fingertip-to-floor test. The sample was stratified by presence/absence of radicular pain (categorized by the dichotomous slump test).
Results: In the entire sample, fair correlations were found between both physical impairment tests (ie, SLR test and flexion ROM) and self-reported disability (.27<r>.44). After stratification by sex, the correlation between RMDQ and flexion ROM and between RMDQ and nonside-specific SLR test increased in women but decreased in men. In those with radicular pain, good correlations were found between RMDQ and flexion ROM (r=.68 for men and r=.70 for women), and moderate correlation was found between the RMDQ and SLR tests of the affected side in women (r=.60), but only fair correlation was found between the RMDQ and SLR tests of the affected side in men (r=.28).
Conclusions: After stratification by sex and presence/absence of radicular pain, the present study supports a good validity of the fingertip-to-floor test for both men and women with radicular pain. The SLR test, however, was of less value as an indicator of self-reported disability after stratification, especially for men.