Occupational asthma follow-up--which markers are elevated in exhaled breath condensate and plasma?

To search for optimal markers in the exhaled breath condensate (EBC), plasma and urine that would reflect the activity/severity of occupational asthma (OA) after the withdrawal from the exposure to the allergen.

Markers of oxidative stress: 8-iso-prostaglandin F2α (8-isoprostane, 8-ISO), malondialdehyde (MDA), 4-hydroxy-trans-2-nonenale (HNE), cysteinyl leukotrienes (LT) and LTB4 were determined using liquid chromatography and mass spectrometry in 43 subjects with immunological OA (49.3 ± 11.8 years), removed from the exposure to the sensitizing agent 10.5 ± 6.5 years ago; and in 20 healthy subjects (49.0 ± 14.9 years). EBC was harvested both before and after the methacholine challenge test. In parallel, identical markers were collected in plasma and urine. The results were analyzed together with forced expiratory volume in one second (FEV1), blood eosinophils, immunoglobulin E (IgE) and eosinophilic cationic protein (ECP) and statistically evaluated (Spearman rank correlation rS, two- or one-sample t tests and alternatively Kruskal Wallis or pair Wilcoxon tests).

Several parameters of lung functions were lower in the patients (FEV1% predicted, MEF25% and MEF50%, Rtot%, p < 0.001). Shorter time interval since the removal from the allergen exposure correlated with higher ECP (rS = 0.375) and lower FEV1%, MEF25% and MEF50% after methacholine challenge (rS = -0.404, -0.425 and -0.532, respectively). In the patients, IgE (p < 0.001) and ECP (p = 0.009) was increased compared to controls. In EBC, 8-ISO and cysteinyl LTs were elevated in the asthmatics initially and after the challenge. Initial 8-ISO in plasma correlated negatively with FEV1 (rS = -0.409) and with methacholine PD20 (rS = -0.474). 8-ISO in plasma after the challenge correlated with IgE (rS = 0.396).

The improvement in OA is very slow and objective impairments persist years after removal from the exposure. Cysteinyl LTs and 8-ISO in EBC and 8-ISO in plasma might enrich the spectrum of useful objective tests for the follow-up of OA.