Establishment of Population Specific Reference Intervals in Healthy Pakistani Adults for 21 Routine and Special Haematology Analytes.

Background: The reference interval (RI) is an interval between two limits derived from distribution of the results obtained from a sample of the reference population. These population based RIs are of paramount significance for the accurate clinical understanding of the patient's health status. Haematological RIs are heavily influenced by a variety of geographical and environmental factors. Therefore, accrediting bodies also mandate that each laboratory should establish its own RIs in its own population. Methods: This cross-sectional study was conducted at the Department of Pathology and Laboratory Medicine, the Aga Khan University Hospital, Pakistan.Twenty-one routine and special quantitative analytes were measured in adults aged 18-60 years who passed the initial health screening questionnaire. All samples were handled strictly following standard operating procedures. Microsoft Excel and EP Evaluator software were used for statistical analysis. Nonparametric CLSI EP28-A3C method was used to establish upper and lower confidence limits at 90% significance. Results: A total of 323 participants passed the questionnaire and were short-listed for blood collection. There were 147 males and 176 females. Reference intervals were established in 297 participants after exclusion of 26 outliers with grossly abnormal test results. Analytes included: 8 red, and 12 white blood cell parameters, platelet count, immature platelet fraction, erythrocyte sedimentation levels, haemoglobin A and A2 levels and glucose-6-phosphatase dehydrogenase levels. Conclusion: Routine and special haematology RIs established in this study reflect significant differences from RIs in Caucasian population. For meaningful interpretation of test results, each haematology laboratory should establish or verify RIs in the population it serves.