Delay in Specimen Processing-Major Source of Preanalytical Variation in Serum Electrolytes

Objective: To evaluate the stability of electrolytes in serum samples due to delay in analysis in a tertiary care government hospital in India, and the maximum time delay acceptable between sample centrifugation and analysis. Materials and Methods: We estimated serum electrolytes of 400 samples with different time intervals between centrifugation and sample analysis on automated analyser. Results: Values were compared using repeated measure ANNOVA and acceptable limit change using in house QC values of 6 months. During the time interval between centrifugation and sample analysis, the samples were kept uncovered in sample cups in the laboratory. Potassium values show significant changes within 1 h (T1, p<0.01) but sodium (T2, p <0.01) and chloride (T2, p <0.001) values are acceptable up to a time delay of 3 h between sample centrifugation and analysis. Conclusion: Samples for electrolytes should be analysed within 1-2 h of centrifugation and if there is any delay in analysis, the samples should be stored under proper conditions.