Bayesian analyses demonstrate tissue blood volume is not decreased during acute sickle cell pain episodes: A preliminary study

BACKGROUND: Pain is the most common complication of Sickle Cell Disease (SCD). Tissue oximetry properties in SCD during steady state and acute pain are not well described. METHODS: This was a cross sectional study of tissue oximetry properties in individuals with SCD during steady state, acute pain and healthy controls without SCD. A novel tissue oximetry device was used to better account for tissue pigmentation interference. We hypothesized that during acute SCD pain, blood volume to painful areas would be at least 10% less than steady state. Bayesian analyses of the data (with flat piors) were planned a priori because of the small projected sample size. RESULTS: The sample included 14 individuals (4 during crisis, 5 steady state, and 5 controls). In individuals with SCD, blood volume to the lower back was higher during crisis (0.18% of tissue volume vs. 0.14%). Bayesian analyses yielded a 3% probability that our hypothesis (that blood volume would decrease by 10%) was correct. CONCLUSIONS: During acute SCD pain, blood volume to painful areas is not decreased. Bayesian analyses were useful for interpretation of small sample data and may have utility in early phase trials for rare diseases.