Fingertip-to-floor test and straight leg raising test: validity, responsiveness, and predictive value in patients with acute/subacute low back pain

Objectives: To investigate the validity over time of the fingertip-to-floor test (FTF) and the straight leg raising test (SLR) using the Roland Morris Disability Questionnaire (RMDQ) and correlation coefficient (r), and to assess the predictive value of factors related to the change in RMDQ over 12 months using multivariate regression analysis.

Design: Longitudinal study.

Setting: Outpatient physical therapy clinic.

Participants: Subjects (N=65) with acute/subacute low back pain (≤13 wk of symptoms). Thirty-eight (58%) had radicular pain as determined by the slump test.

Interventions: Not applicable.

Main outcome measures: Self-reported disability was used as a reference variable and was measured using the RMDQ at baseline and after 1 and 12 months. The FTF and SLR were measured at baseline and after 1 month. Responsiveness and imprecision were assessed by using effect size (ES) and minimal detectable change (MDC). The sample was stratified by the presence or absence of radicular pain (categorized by the slump test).

Results: The change in FTF results was significantly correlated to the 1-month change in RMDQ, both in the entire sample (r=.63) and in the group with radicular pain (r=.66). Similar analysis for the SLR showed a weak relationship to RMDQ. FTF showed adequate responsiveness (ES range, 0.8-0.9) in contrast to SLR (ES range, 0.2-0.5). The MDC for FTF and SLR were 4.5 cm and 5.7°, respectively. The change in FTF results over 1 month was independently more strongly associated with the 12-month (R(2)=.27-.31) change in RMDQ than any of the other variables and multivariate combinations.

Conclusions: Our results suggest that the FTF has good validity in patients with acute/subacute low back pain and even better validity in those with radicular pain. The change in FTF results over the first month was a valid predictor of the change in self-reported disability over 1 year. In contrast, the validity of SLR can be questioned in the present group of patients.