Population-based reference intervals for lipid function tests in pregnant and non-pregnant women in Nairobi City, Kenya.

Background: Accurate interpretation of clinical laboratory test results relies on the application of appropriate reference intervals, which differs between populations. Despite this, there is no Kenyan-derived reference values for clinical management of both pregnant and non-pregnant women, potentially leading to diagnostic misclassification. This study established age- and trimester-specific reference intervals for lipid function tests and compare them with the current practice cut-offs. Methods: Lipid parameters were determined in non-pregnant and pregnant women aged 19-29 and 30-40 years, partitioned by trimester. The measured parameters included total cholesterol, low and density lipoproteins, triglycerides, non-high-density lipoproteins, and their ratios. Differences between groups were assessed using Kruskal-Wallis and Mann-Whitney U tests. Out-of-range analysis were performed between the newly developed reference intervals and the current practice reference values. Results: Significant age- and trimester-specific differences were noted in total cholesterol, low-density lipoproteins, triglycerides, and lipid ratios (p < 0.05), with incremental increases observed in later trimesters. High-density lipoproteins showed variable changes. Out-of-range comparison show significant misclassification: 54 % of pregnant women aged 30-40 years in the trimester two exceeded current low-density lipoproteins reference intervals, while 60 % were misclassified for triglycerides in third trimester. Remarkably, 100 % of women across all groups fell outside the standard high-density lipoproteins reference limits. Conclusion: The current practice reference intervals are inappropriate for clinical assessment of pregnant and non-pregnant women in Nairobi, Kenya. Establishing age- and trimester-specific reference intervals provides a more accurate clinical decision-making tool, enhancing maternal care.