Newly Developed Automated Immunoassay Analyzed

Dipeptidyl peptidase-4 (DPP-4) may be a suitable biomarker to identify people with severe asthma who have greater activation of the interleukin-13 (IL-13) pathway and may therefore benefit from IL-13-targeted treatments.

Increased IL-13 messenger RNA (mRNA) expression and protein concentration in bronchial biopsies, sputum and bronchoalveolar lavage fluid from patients with asthma, compared with healthy individuals, supports a role for IL-13 in the pathophysiology of some types of asthma.

A team of scientists collaborating with those at the Abbott Laboratories (Abbott Park, IL, USA) obtained serum samples from healthy volunteers and from subjects with asthma and type 1 diabetes. They used in DPP-4 concentration assessments, samples obtained from a Phase IIb study of tralokinumab in subjects with severe uncontrolled asthma receiving concomitant high-dose fluticasone and salmeterol. Additional samples, collected for a pre-analytical in-house study to confirm specimen-handling procedures, were provided by consenting volunteers with self-reported asthma.

The team assessed assay performance, utilizing analyses of precision, linearity and sensitivity; interference from common endogenous assay interferents, and from asthma and anti-diabetic medications, were also assessed. The new automated IUO DPP-4 immunoassay was performed on Abbott’s ARCHITECT i System. The immunoassay measurement of DPP-4 has a range from 109 ng/mL to 580 ng/mL. The assay is fully automated with a throughput of 200 tests per hour.

The investigators reported that the total precision of DPP-4 concentration measurement, determined using percentage coefficient of variation, was ≤5% over 20 days. Dilution analysis yielded linear results from 30 to 1,305 ng/mL; the limit of quantitation was 19.2 ng/mL. No notable endogenous or drug interferences were observed at the expected therapeutic concentration. Median DPP-4 concentrations in healthy volunteers and subjects with asthma or Type 1 diabetes were assessed, with concentrations remaining similar in subjects with diabetes and asthma across different demographics.

The authors concluded that their analyses indicate that the ARCHITECT DPP-4 immunoassay is a reliable and robust method for measuring serum DPP-4 concentration. The assay is currently being applied to assess the clinical utility of DPP-4 as a predictive biomarker in Phase III studies of tralokinumab in subjects with uncontrolled asthma. The study was published online on October 20, 2017, in the journal Practical Laboratory Medicine.