Criterion validity of the functional status and pain assessment scale versus pain and length of stay in hospitalized adults with SCD

Abstract Objectives In prior research we demonstrated face, construct, discriminant, and preliminary convergent validity of the newly developed, 10-item Functional Status Pain Assessment (FSPA) scale (0-50) in adult SCD patients hospitalized with VOC. We aimed in this study to further demonstrate criterion validity of the FSPA. Methods This was a prospective observational study of 561 daily functional and pain assessments from 91 hospitalized adults with SCD from January 2018 to June of 2019. Principal Component Analysis (PCA) Partial Least Squares (PLS) models determined the relationship between LOS, pain intensity, and FSPA. A Generalized Linear Model (GLM) to quantified the impact of changes in pain intensity on LOS. Results The population mean age was 34 ± 12.2 years, and 59.3% were female. A little over half were genotype SS. Neither admission nor discharge FSPA scores were significant determinants of LOS. Specifically, no component or factor of FSPA score on day of admission explained the LOS. In addition, FSPA score on day of discharge explained only 5.69% of the variance in LOS. Similarly, FSPA score explained only 19.66% of the variance in pain intensity on any pain day. There was no relationship between LOS and pain intensity changes from admission to discharge (P = .92). Conclusions The FSPA score did not demonstrate criterion validity with respect to NRS pain intensity changes from admission to discharge, nor to the LOS for SCD admissions. Instead, unmeasured, perhaps environmental, psychosocial, and economic variables, exerted a far more substantial influence on hospital LOS.