Effects of a plasma heating procedure for inactivating Ebola virus on common chemical pathology tests

The recent declaration of Ebola virus disease as epidemic by the World Health Organization indicates urgency for affected countries and their laboratories to evaluate and provide treatment to patients potentially infected by the Ebola virus. A heat inactivation procedure involving treating specimens at 60°C for 60 minutes has been suggested for inactivation of the Ebola virus. This study aimed at evaluating the effect of plasma heating on common biochemical tests.

Comparative experimental study.

A regional chemical pathology laboratory in Hong Kong.

Forty consecutive plasma specimens for general chemistry analytes on Beckman Coulter AU5822 and another 40 plasma specimens for troponin I analysis on Access 2 Immunoassay System were obtained, anonymised, and divided into two aliquots. One aliquot was analysed directly and the other was analysed after heating at 60°C for 60 minutes.

A total of 20 chemical pathology tests were evaluated. Nine tests (sodium, potassium, chloride, urea, creatinine, total calcium, phosphate, total protein, and glucose) were not significantly affected by the heat inactivation procedure and remained clinically interpretable. Results for magnesium (15% mean increase), albumin (41% mean increase), bilirubin (8% mean decrease), amylase (27% mean decrease), and troponin I (76% mean decrease) were still interpretable using regression estimation with proportional bias. However, all enzymes studied except amylase (alanine transaminase, aspartate transaminase, alkaline phosphatase, gamma-glutamyltransferase, creatine kinase, and lactate dehydrogenase) were inactivated to a significant degree. Their Pearson r or Spearman rho values ranged from no significant correlation (P≥0.05) to 0.767, and most normality was rejected.

Heat inactivation results in no significant change in electrolytes, glucose, and renal function tests, but causes a significant bias for many analytes. Recognition of the relationship between pre- and post-heat inactivation specimens allows clinical interpretation of affected values and contributes to patient care. For safety and diagnostic accuracy, we recommend use of a point-of-care device for blood gases, electrolytes, troponin, and liver and renal function tests within a class 2 or above biosafety cabinet with level 3 or above biosafety laboratory practice.