Chief Medical Officer Our Blood Institute Little Rock, Arkansas, United States
Background/Case Studies: Clinical laboratory tests require appropriate reference intervals (RI) for accurate interpretation. The importance of RI cannot be understated as many diagnostic and medical treatment decisions are based on laboratory results. Blood centers are ideal locations for reference subject recruitment since blood donors are diverse and vary in age, race, ethnicity, reasonable health status, etc. Interleukin-6 (IL-6) is a pro-inflammatory cytokine that is elevated in various diseases including rheumatoid arthritis, juvenile idiopathic arthritis, and COVID-19. In severe COVID-19 infections, IL-6 levels are 2.9 times higher compared to mild cases, making it a potential therapeutic target and prognostic indicator for moderate-to-severe COVID-19. An independent blood center leveraged access to a large and diverse donor population to evaluate the RI of IL-6 in the community using a new point-of-care (POC) testing device.
Study
Design/Methods: Whole blood (WB) and serum samples were taken from healthy adults aged > 22 years who donated blood at a regional blood center from September to December 2022. IL-6 testing was run on samples using a POC microfluidic immunoanalyzer. Participants were enrolled based on IRB-approved, study-specific inclusion/exclusion criteria. The POC device RI was compared to a peer-reviewed publication on normal values for IL‐6 in healthy individuals (https://pubmed.ncbi.nlm.nih.gov/33155686/).
Results/Findings: A total of 185 donors were screened, of whom 134 were eligible for the study. Most participants were male (58.2%) and Caucasian (76.1%). IL-6 ranges in WB were significantly higher than serum levels, 1–285 pg/mL versus 0–185 pg/mL, (Wilcoxon p< 0.001) (Table 1). The difference between males and females was significant for WB IL-6 (Mann-Whitney p=0.001), but not for serum IL-6 (p=0.123). The measured IL-6 values positively correlated with age (correlation coefficient WB 0.227 [p=0.008]; serum 0.197 [p=0.022]). The POC immunoanalyzer has a specificity of 93% (WB) and 94% (serum) when testing for any evidence of disease or inflammation, using a cutoff value based on the 1st Standard Deviation. Conclusions: Blood centers are ideal locations for determining normal community RI for various laboratory tests. Testing of IL-6 using a POC device showed that the RI for WB was within the RI established by a previously published manuscript. Serum RI was lower than WB in the healthy adult population, but no RI for serum IL-6 has been previously published. Specificity levels were comparable to those of commonly used POC tests, indicating clinical utility for IL-6 using this new POC device.
Importance of research: Reference intervals (RI) are essential for clinical laboratory test interpretation and patient care as many clinical decisions are based on laboratory testing. RI testing is challenging to perform and because of these difficulties, most laboratories elect not to establish their own RIs, but rather choose to verify RIs that have been reported by the manufacturer or as established by another laboratory. This abstract demonstrates how blood centers can ease the burden of this challenge.
