Indirect Determination of Hematological Reference Intervals in Healthy Moroccan Adults Using Outpatient Data

Background: Reference intervals are essential for the interpretation of clinical laboratory tests and patient management. This study aims to determine age and gender reference intervals of complete blood count (CBC) in the Moroccan population by using the indirect approach. Methods: The study used data of ostensibly healthy adults collected retrospectively using the laboratory information system (LIS) of the Laboratory for Research and Medical Analysis of the Fraternal Royal Gendarmerie in Rabat (Morocco), between January 2018 and February 2020. The study included 5,898 men and 10,172 women ranging in age from 18 to 90 years. The lower and upper reference limits of CBC parameters were calculated using the nonparametric technique, as suggested by the Clinical and Laboratory Standards Institute (CLSI). Results: All hematological parameters showed no clinically significant gender -related differences, except small differences in the values of hemoglobin (HB), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC). There were also no clinically significant agerelated differences for median values of all hematology analytes in both genders, except for platelet count (PLT) that continued to decline with increasing age in men and women, and Red blood cell count (RBC), Hematocrit (HCT), and hemoglobin (HB) that tended to increase with age but decrease in older age groups in men while they tended to increase with age in women. Conclusions: The indirect method can be used to establish reference intervals for CBC, with appropriate selection criteria and statistical tools. Our findings differed from the reference ranges provided in the textbook and also in other countries' reports.