Background Locally established clinical laboratory reference intervals (RIs) are required to interpret laboratory test results for screening, diagnosis and prognosis. The objective of this study was establishing reference interval of clinical chemistry parameters among apparently healthy adolescents aged between 12 and 17 years in Mekelle, Tigrai, northern part of Ethiopia. Methods Community based cross sectional study was employed from December 2018 to March 2019 in Mekelle city among 172 males and 172 females based on Multi stage sampling technique. Blood samples were tested for Fasting blood sugar (FBS), alanine aminino transferase (ALT), aspartate amino transferase (AST), alkaline phosphatase (ALP), Creatinine, urea, total protein, albumin (ALB), direct and indirect bilirubin (BIL.D and BIL.T) using 25 Bio system clinical chemistry analyzer. Results were analyzed using SPSS version 23 software and based on the Clinical Laboratory Standard Institute (CLSI)/ International Federation of Clinical Chemistry (IFCC) C 28-A3 Guideline which defines the reference interval as the 95% central range of 2.5 th and 97.5 th percentiles. Mann Whitney U test, descriptive statistics and box and whisker were statistical tools used for analysis.

Background Hematological reference intervals are important in clinical and diagnostic management for the assessment of health and disease conditions. Hematological reference intervals are better to be established based on gender and age differences as these are among the main affecting factors. Objective The aim of this study was to establish hematological reference intervals among apparently healthy adolescents aged 12–17 years in Mekelle City, Tigrai, Northern Ethiopia, 2019. Method A community-based cross-sectional study was conducted in 249 adolescents aged 12–17 years from December 2018 to May 2019. About 4ml of blood sample was collected from each study participant using vacutainer tube containing K 2 EDTA. Hematological parameters were analyzed using Sysmex KX-21N hematology analyzer (Sysmex Corporation Kobe, Japan). Data were entered and analyzed using SPSS version 23. Both parametric and non-parametric analyses were used to calculate the median and 95% of reference intervals. The 97.5 th and 2.5 th percentiles were calculated using descriptive statistics for the upper and lower reference limits of the study participants. Differences in reference intervals between male and female participants were evaluated using the Mann–Whitney U test. Result Among the 249 participants 122 (49%) were males and 127 (51%) were females with the median age of 14.5 (range 12 to 17) years were recruited in this study. The median and the 95% reference intervals of hematological parameters were determined. The 95% RIs were: Red blood cells (10 12 /Liter) 4.6–5.9 (Males) and 4.3–5.6 (Females), White blood cells (10 9 /Liter) 2.9–9.6 (Males) and 3.4–10.2 (Females), Hemoglobin (g/dl) 12.6–17.1 (Males) and 12–15.4 (Females), Platelets (10 9 /Liter) 138–364 (Males) and 151–462 (Females). Almost all of the hematological parameters showed significant differences (p<0.05) across gender. Conclusion The hematological reference intervals established in this study showed a difference based on gender. We suggest preparing and using distinct local reference intervals for males and females separately.