Effects of storage temperature and delayed analysis on routine biochemical and haematological test results

Blood samples collected in primary care may be transported to central laboratories, creating variable intervals between collection, processing and analysis. This study evaluated the effects of delayed analysis and storage temperature on routine biochemical and haematological test results under controlled laboratory conditions, with relevance to specimen handling and transport in primary care. This prospective, controlled, repeated-measures laboratory study included 32 healthy volunteers (16 women and 16 men) at Van Yüzüncü Yıl University Dursun Odabaş Medical Centre, Türkiye. Serum and ethylenediaminetetraacetic acid whole-blood specimens were stored at room temperature (18–24 °C) or 4 °C. Twenty-seven biochemical and 26 complete blood count parameters were measured at a common baseline and after 4, 8 and 24 h. Time effects were assessed separately for each storage condition using Friedman tests, followed by Wilcoxon signed-rank tests with Holm adjustment. Storage conditions were compared at each follow-up time using paired Wilcoxon signed-rank tests. Benjamini-Hochberg false discovery rate correction was applied to multiple testing. Statistical analyses were performed using Python and the SciPy scientific computing library. Delayed analysis produced time-dependent changes in several biochemical and haematological parameters, with the magnitude of change varying according to storage condition. At 24 h at room temperature, haematocrit increased by 7.61%, mean corpuscular volume by 7.51% and red cell distribution width-standard deviation by 15.95%, whereas mean corpuscular haemoglobin concentration decreased by 7.11%. Corresponding changes in these erythrocyte-related indices were substantially smaller at 4 °C. Platelet indices changed under both conditions, with mean platelet volume increasing by 4.85% at room temperature and 6.85% at 4 °C, and platelet large cell ratio increasing by 17.34% and 23.72%, respectively. Among biochemical analytes, triglycerides increased by 14.75% at room temperature and 11.55% at 4 °C, while total iron-binding capacity increased by 11.15% and 8.86%, respectively. Delayed analysis and storage temperature were associated with measurable changes in several routine biochemical and haematological test results. Refrigerated storage generally reduced time-dependent changes in several haematological parameters compared with room-temperature storage, although changes were also observed at 4 °C. These findings highlight the importance of considering both storage temperature and analysis delay when handling specimens collected in primary care. The statistically significant changes observed should not be interpreted as formal analytical or clinical stability thresholds.