A highly sensitive immunoassay for interleukin-6 in dried blood spots

Interleukin-6 (IL-6) is a pro-inflammatory cytokine that is associated with the production of C-reactive protein, the acute phase response, and chronic low-grade inflammation. In this report, we describe and validate a highly sensitive enzyme-linked immunosorbent assay (ELISA) for quantifying IL-6 at low concentrations in samples of capillary whole blood collected from a simple finger stick and dried on filter paper (dried blood spots, DBS).

A commercially available ELISA for IL-6 was modified to develop a protocol for the quantification of IL-6 in DBS samples. Procedures for sample elution and incubation were optimized for precision, reliability, accuracy, and lower limit of detection using small volumes of DBS. A set of 46 matched serum/DBS samples were used to evaluate agreement between serum and DBS results.

The protocol demonstrated acceptable levels of precision, reliability, accuracy, and agreement with serum-based results. The lower limit of detection was sufficiently low to measure levels of IL-6 associated with both chronic, low-grade inflammation, and acute increases in inflammatory activity.

This protocol adds to the growing panel of analytes validated for quantification in DBS samples and should facilitate future research on the causes and consequences of inflammation in diverse non-clinical settings.