Reporting of acute low back pain in a telephone interview. Identification of potential biases.

STUDY DESIGN: This was a survey of 235 individuals with and 132 individuals without documented low back pain.

OBJECTIVES: To approximate the magnitude of potential reporting biases in estimates of prevalence of and medical care use in low back pain.

SUMMARY OF BACKGROUND DATA: The use of survey techniques presents several possible biases in the reporting of acute symptoms. These biases are especially pertinent in musculoskeletal symptoms, which often are recurrent and not life-threatening.

METHODS: Two-hundred-thirty-five patients with acute low back pain were contacted by telephone 4-16 months after their physician visit and surveyed regarding the presence and date of back pain episodes. One-hundred-thirty-two patients who had no functionally disabling back pain on physician interview were interviewed.

RESULTS: Of the patients who had sought care for back pain, 21% indicated they had not had back pain when interviewed 4-16 months later. Episodes of pain that occurred more than 8 months before the interview tended to be recalled as occurring more recently than they actually occurred, confirming "forward telescoping" of the illness episode. Only 3% of the individuals without functionally impairing pain reported such pain on a separate interview.

CONCLUSIONS: Lack of recall occurs regarding acute low back pain, usually a self-limited illness. This potential under-estimate of back pain prevalence may be balanced by forward telescoping of the date of illness occurrence.