The Stability of Never Thawed Serum Samples Stored in Liquid Nitrogen: Data from the National Health and Nutrition Examination Survey, 1999–2000 and 2005–2006

• Activity Number: 87 - Survival and Longitudinal/Clustered Data Analysis
• Type: Contributed
• Date/Time: Monday, August 9, 2021 : 10:00 AM to 11:50 AM
• Sponsor: Biometrics Section
• Author(s): Jennifer Rammon* and Eric Tolliver and Renee Storandt and Geraldine M McQuillian
• Companies: National Center for Health Statistics/CDC and U.S. Food and Drug Administration and National Center for Health Statistics/CDC and National Center for Health Statistics/CDC
• Keywords: NHANES; biospecimen; serum samples; biomarker; Deming regression; clinical chemistry

Abstract

The effect of prolonged storage (13–20 years) on laboratory test results is examined in the NHANES biospecimen collection to determine whether there is evidence of sample degradation under liquid nitrogen storage conditions. Measurements taken at the time of the original venipuncture in 1999–2000 or 2005–2006 are compared to 2018–2019 post-thaw measurements from the same survey participant and venipuncture for systematic random sub-samples of the following analytes: nonsmoking cotinine, smoking cotinine, methylmalonic acid (MMA), vitamin A, vitamin E, and Hepatitis C virus (HCV-RNA). Biospecimen degradation is assessed using difference plots, t-tests, and Deming regression models for quantitative analytes and using concordance measures and McNemar’s test for HCV-RNA. We observe proportional differences of 10-12% for cotinine (smokers and non-smokers alike), 5-8% for vitamin A, and 9-12% for vitamin E, a constant difference of 8-16% for MMA, and 99% concordance between the two measurements for HCV-RNA. Differences are statistically significant for all quantitative analytes and statistically insignificant for HCV-RNA. From a clinical perspective, differences are not large.