A-193 Effects of Delayed Centrifugation and Delayed Testing on the Stability of Comprehensive Metabolic Profile Analytes
Authors: Chan C W , Gant Kanegusuku A , Yeo K J 
Published: September 2023

Abstract

Background
The centralization of clinical laboratory testing has become increasingly common in recent years. While centralization allows for consolidation of resources, expanded test menus, procedural standardization, and improved efficiencies, central laboratories can face significant logistical challenges related to sample transport. In particular, problems may arise when samples are received from distant sites or if the courier services used to transport samples are infrequent or unreliable. Policies aimed to mitigate pre-analytical issues such as the time-to-centrifugation, the time-to-testing, and storage temperature, are best devised when driven by empiric data.

Objective
In this study, we provide stability studies for the Comprehensive Metabolic Panel (CMP) analytes in paired serum and lithium heparin (LiHep) plasma samples. Our findings not only complement preexisting literature data but also help guide the current sample acceptance criteria and policy for receiving satellite clinic samples in our laboratory.

Methods
Serum and LiHep plasma were collected from healthy volunteers in gel separator tubes. In one set of experiments, samples of both specimen types were all centrifuged within 30 min of collection and tested at pre-determined time intervals (2, 4, 6, 12, and 24 h post collection) using Roche Cobas 8000 system. In a second set of experiments, samples of both specimen types collected from another set of volunteers were kept at room temperature and only centrifuged prior to testing at pre-determined time intervals (2, 4, 6, 12, and 24 h post collection). Sample storage prior to testing was at room temperature. The percent recovery of each result was calculated relative to the first sample of the series. The CMP includes the following analytes: glucose, sodium, potassium, chloride, carbon dioxide, urea nitrogen, creatinine, calcium, total bilirubin, total protein, albumin, alkaline phosphatase, aspartate aminotransferase (AST), and alanine aminotransferase (ALT).

Results
Glucose in promptly centrifuged (i.e., within 30 min of collection) LiHep plasma samples showed acceptable recovery (≥90%) when tested within 12 h of collection in LiHep gel separator tubes, whereas glucose stability in serum stored at room temperature exceeded 24 h. In contrast, delayed centrifugation beyond 3 h led to unacceptably low recoveries in both LiHep plasma and serum sample types. All other analytes included in the CMP were stable beyond 24 h irrespective of whether the sample type is LiHep plasma or serum, or even if the time-to-centrifugation was up to 24 h.

Conclusions
Based on the study, our laboratory has updated our policy to accept pre-centrifuged (i.e., within 30 min of collection) LiHep plasma from satellite clinics up to 8 h from blood collection, which is a 2-hour increase as compared to our prior cut-off acceptability. Given the location of our satellite clinics and unpredictability of sample transport, this increase represents a positive change in reducing outpatient sample rejections while ensuring reliable laboratory results.