Reference Interval for Serum L-Homoarginine Determined with Enzyme-Linked Immunosorbent Assay in the Population-Based Study of Health in Pomerania

Abstract

Abstract Background Low levels of the endogenous amino acid L-homoarginine are a risk factor for cardiovascular morbidity and mortality. For individual risk prediction, commercially available test systems are mandatory. This study aims at formulating sex- and age-specific reference intervals of serum L-homoarginine determined with an ELISA. Methods We determined reference intervals for serum L-homoarginine stratified by age and sex in a sample of 1285 healthy participants of the Study of Health in Pomerania (SHIP)-TREND cohort after exclusion of participants with cardiovascular diseases, diabetes mellitus, hypertension, metabolic syndrome, elevated liver enzymes, chronic kidney disease stages III or IV, or body mass index >25 kg/m2. Serum L-homoarginine was determined applying a commercially available ELISA. Results The reference cohort included 836 women (median age 41, 25th and 75th percentiles are 32 and 50 years) and 449 men (median age 38, 25th, and 75th percentiles are 30 and 49 years). The median serum concentration of L-homoarginine was 1.93 (25th 1.49; 75th 2.60) µmol/L in women and 2.02 (25th 1.63; 75th 2.61) µmol/L in men (P = 0.04). The reference intervals (2.5th to 97.5th percentile) were 0.89–5.29 µmol/L for women and 1.09–3.76 µmol/L for men. The L-homoarginine serum concentration declined over age decades in both sexes and a notable interaction with sex hormone intake in women was observed. Conclusions The novelty of our study is that we determined reference intervals specific for the L-isomer being lower than those previously reported for homoarginine in SHIP and thus might be helpful in identifying individuals suitable for oral L-homoarginine supplementation.