Is self-reported symptom duration in individuals with patellofemoral pain an accurate measure? An observational longitudinal study.

BACKGROUND

Although self-reported symptom duration of individuals with patellofemoral pain (PFP) is usually assessed for clinical and research purposes, its accuracy has never been investigated.

OBJECTIVES

We followed up individuals with PFP over 15 months to determine the agreement between self-reported symptom duration and calculated symptom duration.

METHODS

Self-reported symptom duration of 39 participants was assessed at baseline and re-assessed at follow-up. Calculated follow-up symptom duration was determined by the summation of baseline self-reported symptom duration with the known follow-up duration. The symptom duration difference was determined by the subtraction of the calculated follow-up symptom duration and the self-reported follow-up symptom.

RESULTS

We identified a symptom duration difference of 20.1 months (95 % confidence interval: 11.2, 29.1 months), with greater differences in individuals with longer symptom duration (r² = 0.12).

CONCLUSION

Our findings suggest that the accuracy of self-reported symptom duration measures in individuals with PFP is questionable and techniques should be used to improve it.