Predictive ability of intermittent daily sickle cell pain assessment: The PISCES project

Background. Pain diary assessment in sickle cell disease (SCD) may be expensive and impose a high respondent burden. Objective. To report whether intermittent assessment could substitute for continuous daily pain assessment in SCD. Design. Prospective cohort study. Setting. Academic and community practices in Virginia. Patients. A total of 125 SCD patients age 16 years or older in the Pain in Sickle Cell Epidemiology Study. Measurements. Using pain measures that summarized all diaries as the gold standard, we tested the statistical equivalence of four alternative strategies that summarized diaries only from the week prior or the month prior to study completion; one week per month; or one day per week (random day). Summary measures included percent pain days, percent crisis days (self-defined), mean pain (0–9 Likert scale) on all days, and mean pain on pain days. Equivalence tests included comparisons of means, regression intercepts, and slopes, as well as measurement of R². Results. Compared with the gold standard, the one-day-per-week and one-week-per-month strategies yielded statistically equivalent means of six summary pain measures, and the week prior and month prior yielded equivalent means as some of the measures. Regression showed statistically equivalent slopes and intercepts to the gold standard using one-day-per-week and one-week-per-month strategies for percent pain days and percent crisis days, but almost no other equivalence. R² values ranged from 0.64 to 0.989. Conclusions. It is possible to simulate five- to six-month daily assessment of pain in SCD. Either one-day-per-week or one-week-per-month assessment yields an equivalent mean and fair regression equivalence.