What interval of daily pain assessment is required to reliably diagnose chronic pain in SCD? The Pain in Sickle Cell Epidemiology Study

Objectives: Chronic pain in SCD has been defined as pain on most days over 6 months. In the landmark Pain in Sickle Cell Epidemiology Study, 60% of patients submitted <5 of the expected 6 months of pain diaries. Identifying chronic SCD pain using this long daily assessment interval is impractical. We therefore examined whether shorter, less burdensome intervals could accurately identify chronic SCD pain. Methods: As the gold-standard sample, we chose the 116 Pain in Sickle Cell Epidemiology Study patients who submitted >5 months of diaries (153) and >49% of diaries during all months from 1 to 4. Using the same dataset, we tested daily diary assessment over shorter intervals: 2 weeks, 1 month, 2 months, 3 months, and 4 months. We defined chronic pain as intensity rated as >0 on >50% of diary days, regardless of interval. We then calculated the sensitivity and specificity of each diary interval. Results: Among the gold-standard sample, 51.3% of patients had diary-defined chronic pain. Collection intervals of 2 months or more yielded similar chronic pain prevalences with identically high sensitivity (98.3%) and specificity (93%). Intervals of 1 month and 2 weeks yielded increasingly lower specificity (80.7%, 73.7%, respectively), but preserved sensitivity (≥96.6%). Conclusion: In the Pain in Sickle Cell Epidemiology Study, intervals of 2 months or more of daily diary collection yielded high sensitivity and specificity, compared to an interval of 5-6 months. One may reasonably diagnose chronic SCD pain using 2 months of daily diaries.