Effect of refrigeration, room temperature, and processing time on serum immunofluorescent antibody titers for Sarcocystis neurona

Background

Evaluating antibody titers for Sarcocystis neurona for the diagnosis of equine protozoal myeloencephalitis from serum samples is a common practice. However, ensuring timely and proper refrigeration is not always possible.

Objectives

To evaluate immunofluorescent antibody (IFA) titers for S. neurona from serum samples stored at room temperature and 4°C.

Samples

Twenty-two serum samples.

Methods

Prospective longitudinal study. Two serum aliquots of 1 mL each were stored at room temperature (20-23.3°C) and 4°C. The unrefrigerated aliquot was immediately tested for IFA titers. Both aliquots were retested on Days 5 and 10 after collection. A paired t test was used to compare IFA titers at different time points.

Results

There was no significant difference between IFA titers from baseline with those stored at room temperature at Days 5 (P = .741, 95% CI [−56.83, 78.65]), 10 (P = .677, 95% CI [−50.01, 75.46]), and between 5 and 10 days (P = 0.949, 95% CI [−57.50, 61.14]). There was no significant difference from baseline with those stored at 4°C for Days 5 (P = .964, 95% CI [−81.81, 85.45]), 10 (P = 0.573, 95% CI [−109.4, 62.15]), and between 5 and 10 days (P = .5, 95% CI [−102.6, 51.67]). There was no statistical difference between samples stored at room temperature and 4°C (P = .688, CI [−55.51, 37.33]) on Days 5 and 10 (P = .104, CI [−80.8, 8.07]).

Conclusions and Clinical Importance

Immunofluorescent antibody test titers for S. neurona are stable for up to 10 days at room temperature and 4°C.