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Pentraxin 3 stability in serum and urine samples at -20 °C during a 4-week period
Igor Alfirevic1,2,3, Helena Cicak4, Andrea Saracevic4
1University Department of Surgery, University Hospital Sveti Duh, Zagreb, Croatia.
Introduction:
The aim of our study was to examine the stability of pentraxin 3 (PTX3) in serum and urine samples during 4-week storage at -20 °C.
Methods:
Ten routine leftover serum and urine samples were used in this study. The samples were stored at -20 °C over 4 weeks and analyzed each week in a single batch using the Human pentraxin 3 ELISA kit (BioVendor Group). Stability was expressed as a percentage difference between the initial measurement and the measurements taken weekly. Total error (33%) was used as the performance criterion for stability.
Results:
The concentration of PTX3 decreases with time during storage at -20 °C in both serum and urine. The percentage difference exceeded the set criterion in serum samples at the third week of storage (percentage difference = -23.5% [95% CI, -36.6% to -10.5%]) and at the first week of storage in urine samples (percentage difference = -41.5% [95% CI, -63.1% to ‒19.8%]).
Discussion:
Pentraxin 3 can be stored in serum samples for a maximum of 2 weeks at -20 °C before analysis to measure representative results. Because PTX3 is not stable in urine samples, such samples should be analyzed on the day of sample collection.
