Narrowed reference intervals for complete blood count in a multiethnic population

Biological variation studies have shown that the complete blood count (CBC) has narrow within-individual variation and wide group variation, indicating that the use of reference intervals (RIs) is challenging. The aim of this study was to examine differences in CBC RIs according to race/ethnicity in a multiethnic population at a hospital in San Francisco in hopes of improving the medical utility of CBC testing. Subject data were obtained by screening CBC results from the medical records of outpatients meeting certain criteria who visited Zuckerberg San Francisco General Hospital from April 2017 to January 2018. From these records, sex-and race/ethnicity-specific CBC RIs were calculated as the 2.5th to 97.5th percentiles. From a total of 552 subjects, 47.9% were male (65 White, 50 Black, 71 Hispanic and 54 Asian) and 52.1% were female (51 White, 39 Black, 122 Hispanic and 72 Asian). The RIs of neutrophil, lymphocyte and eosinophil counts; and hemoglobin, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) showed significant differences (p<0.05) among the four racial/ethnic groups: neutrophil, lymphocyte and eosinophil counts; and MCHC in males, and hemoglobin, MCV, MCH and MCHC in females. Race/ethnicity-specific CBC RIs should be taken into consideration in a multiethnic population to better interpret patient status and make progress toward precision medicine.