The Transition from Acute to Subacute and Chronic Low Back Pain

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Abstract
Follow-up study. To document differences between acute and subacute low back pain (LBP) based on the risk of developing chronic disability and on the correlation between pain, disability, and quality of life. The subacute stage should identify the time in which the risk of developing chronic disability increases and specific measures should be considered, but its definition is currently inconsistent. 366 patients were given Visual Analog Scales (VAS) for LBP and referred pain (RP), Roland-Morris questionnaires (RMQs), and EuroQol (EQ) questionnaires on their first visit and 14 and 59 days later. Median duration of pain when entering the study was 4 days (P25, P75: 2,10). Simple correlations among LBP, VAS, and RMQ were r = 0.407 (day 1), 0.688 (day 15), and 0.739 (day 60). Among LBP, VAS, and EQ, r = −0.523, r = −0.701, and r = −0.760. Among RP, VAS, and RMQ, r = 0.280, r = 0.561, and r = 0.583. Between RP, VAS, and EQ, r = −0.306, r = −0.534 and r = −0.600. Between RMQ and EQ, r = −0.650, r = −0.765 and r = −0.815. In 42 patients, disability did not improve throughout the study period, and a prestudy duration of ≥14 days was the only independent predictor. All these models were significant at the P < 0.007 level. Improvement in quality of life was more likely to occur in patients in which disability improved [odds ratio (OR), 18.29; 95% CI; 8.64, 38.73; P < 0.001]. As opposed to acute patients, in those with a prestudy duration of pain of ≥14 days, on day 60 RP had no influence on disability, and LBP had no influence on quality of life. LBP influences disability and quality of life more than RP. Disability is predicted by pain duration and quality of life is predicted by disability, but pain severity predicts neither one of them. Changes related to determinants of disability and quality of life, and to the prediction of chronic disability, appear 14 days after the onset of pain, supporting that cutoff point for considering a patient as being subacute.