0028 Systematic Review: Time of day differences in complete blood count values

Abstract Introduction The complete blood count (CBC) is the most commonly ordered test with a large range of reference values that do not consider time day for interpretation. Clinicians are largely unfamiliar influence on CBC values. Our objective was to systematically review this topic report peak and trough timing Methods A systematic search PubMed, Ovid, Scopus, CINAHL, Cochrane, Embase, Web Science performed studies evaluating any part over 24 hours. were screened eligibility based predetermined criteria including: measurement at least 3 points in In total, 164 full-text articles 32 included final analysis. aggregated data analyzed Cosinor package R statistical environment Stata SE create cosinor graphs Forest plots each component CBC, respectively. Results Of articles, metalysis following subsets: leukocytes, erythrocytes, hemoglobin, hematocrit, platelets, neutrophils, lymphocytes, monocytes, eosinophils, basophils. Lymphocytes exhibited statistically significant diurnal rhythm (p=0.014, n=10 articles) 2280.10 cells/uL 23:17 (CI: 1731.80, 2828.40) 1661.49 08:53 1242.64, 2080.33). Erythrocytes, hematocrit peaked morning; while basophils late afternoon early evening; lymphocytes eosinophils night. High heterogeneity results across noted, likely attributable difference circadian factors controlled. Limitations include small sample size limited samples meta analysis, affecting results. Conclusion There changes might be important as we move towards precision medicine. Given number sizes, future work should evaluate sources inform time-dependent interpretation CBC. Support (if any)