Pre-processing stability of routine clinical chemistry analytes in a clotting tube; investigating the (un)suitability for at-home sample collection.

Background: There is a growing interest in self-collection of blood for clinical applications. Next to allowing patients to self-sample blood, adequate sample stability of the analyte is essential to provide an accurate and reliable test result. This is particularly important for self-collected blood, as the transport of the sample to the clinical laboratory will generally require significantly more time than routine blood samples collected by healthcare professionals, and under less controlled circumstances.

Methods: Three additional blood collection tubes (coagulation tubes) were collected from nine patients; one was processed immediately, the second and third were processed after 48 h of storage at 20 °C and 37 °C, respectively. The collected serum was stored at -20 °C and samples collected from individual patients were analyzed in the same analytical run for 18 routine chemistry analytes and the tumor markers PSA and CEA. The recoveries obtained after delayed processing were quantified and the quality of the sample for each analyte was determined using the analytical performance specifications based on biological variation.

Results: For each analyte, the quality level of samples with delayed processing was determined. For the CEA, PSA, CRP, creatinine, HDL-cholestrol, triglycerides and yGT the recovery was within the desirable bias requirement. Recovery for glucose, all included electrolytes, ALT and AST exceeded the minimum bias criterion.

Conclusions: Several analytes including sodium, chloride, potassium, calcium, and liver enzymes were not, while others; CEA, PSA, CRP, creatinine and triglycerides, were found to be sufficiently stable in coagulated blood, when processed with a delay of 48 h.