A-086 Studying Stability of Routine Analytes Reveals a Temperature-Dependent Signature Associated with Factitious Hyperkalemia in Unspun Specimens

Abstract Background Hyperkalemia is a potentially life-threatening condition, and distinguishing between true and factitious hyperkalemia remains a considerable challenge, often leading to inappropriate patient management. In community settings, factitious hyperkalemia is frequently caused by pre-analytical errors such as delayed centrifugation and temperature fluctuations during specimen transportation. Community and reference laboratories, which often receive specimens from healthcare provider offices, are particularly vulnerable to these issues. This study investigated the stability of routine chemistry and immunochemistry analytes under both fixed and variable temperature conditions to establish the maximum permissible duration for delayed centrifugation. Additionally, the study sought to identify routine analyte changes that are associated with factitious hyperkalemia, which could help differentiate it from true hyperkalemia. Methods Serum separator tubes (SSTs) were collected from 260 volunteers and split into four groups. Groups one and two, fifty volunteers each, were used to assess analyte stability in spun and unspun samples stored at fixed temperatures (room temperature (RT) or 4°C). Groups three and four, eighty volunteers each, were used to evaluate analyte stability in spun and unspun specimens exposed to fluctuating temperatures, alternating between -5°C and +35°C. Four to seven specimens were collected from each volunteer. The tubes were centrifuged at baseline (30 minutes post-collection) or at various time intervals within 48 hours of collection. A total of 27 routine analytes were analyzed in each tube using Siemens Advia Chemistry or Centaur systems, and the percentage change in analyte levels from baseline was calculated. Statistical analyses were performed using ANOVA, followed by the Tukey-Kramer Post-Hoc Test. Results No significant changes in analyte levels were observed in spun samples stored at either fixed or variable temperatures, emphasizing the critical importance of timely centrifugation at the point of collection. Delayed centrifugation led to significant and temperature-dependent changes in several analytes. For example, the ex vivo increase in potassium was 14.2 times faster at 4°C than at RT. Bias exceeded the total allowable error after 4 hours of collection when samples were stored at 4°C, though no other analytes showed significant changes during this period. Importantly, we identified a set of temperature-dependent analyte changes associated with factitious hyperkalemia, including glucose, creatinine, LDH, phosphate, iron, urea and uric acid. These changes can serve as a reliable signature to differentiate false potassium elevations from true hyperkalemia, depending on whether the samples were stored at RT or 4°C. Additionally, exposure to fluctuating temperatures did not significantly impact analyte levels in unspun samples when compared to those stored at fixed temperatures. Conclusion Remote specimen collection units should prioritize centrifugation of specimens before sending them for testing. Unspun specimens stored at 4°C remain viable for routine chemistry testing, including potassium, for up to 4 hours post-collection. While potassium remains stable at RT for up to 24 hours, several other analytes undergo significant changes within this period. We have identified a distinct set of analyte changes that can be used as a signature to differentiate factitious from true hyperkalemia, ultimately improving diagnostic accuracy and enhancing patient care.