Abstract Background Clinical laboratory results play an important role in diagnosis, monitoring disease progression, and making informed decisions about the treatment plans of patients. The total testing process can be divided into three phases: pre-analytical, analytical, and post-analytical. The accuracy of laboratory results depends on all three phases of the testing process, however, the pre-analytical phase is a major source of error for clinical labs because it is most difficult to monitor and control. In centralized or referral labs it is important to consider operational challenges in the preanalytical phase such as transport delays and limited staffing that may delay sample analysis beyond stability limits provided by vendors or the literature. Therefore, it is prudent that labs define analyte stability limits based on time and storage conditions to ensure that only clinically actionable results are provided to clinicians. Methods Residual and volunteer samples were collected for Alpha-fetoprotein, Free T4, Free T3, Estradiol, Progesterone, Parathyroid hormone, Cortisol, Beta Human Chorionic Gonadotropin, Prostate-specific Antigen, Thyroid Peroxidase, Carcinoembryonic antigen, Cancer Antigen 125, Testosterone, Follicle Stimulating Hormone, Luteinizing Hormone, Dehydroepiandrosterone sulphate, Prolactin, Thyroid Stimulating Hormone, Vitamin B12, and Ferritin in both pathologic and non-pathologic concentrations to assess stability for 24 and 72 hours. Samples were collected in serum separator tubes (SST) or red-top vacutainers and stored refrigerated in original vacutainers (i.e. stored on cells or gel) or serum aliquots. Stability was assessed by comparing the percent deviation at each time point relative to the baseline result, and interpreted relative to the maximum permissible instability (MPI) using inter and intra-individual biological variation data from the European Federation of Clinical Chemistry and Lab Medicine (EFLM) database. MPI was calculated as: 0.375 v(Cvi2+ CVg2). Results Most of the hormones and tumor markers studied were stable in pathologic and non-pathologic ranges for aliquot samples and the original vacutainers across all time points (Table 1). Vitamin B12 exceeded stability limits by 72 h time point in original vacutainers and serum aliquots. Estradiol was stable for only 24 h of refrigerated storage in the original vacutainer only and these samples should not be sent as an aliquot. Conclusion This study supports an evidence-based process for receiving and storing specimens collected for hormone and tumor markers analysis. These data are useful for all clinical labs to provide accurate patient results when possible and to reduce unnecessary sample rejections and repeated phlebotomy.
Bharti et al. (Wed,) studied this question.
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