Do Low Molecular Weight Agents Cause More Severe Asthma than High Molecular Weight Agents?
BACKGROUND
The aim of this study was to analyse whether patients with occupational asthma (OA) caused by low molecular weight (LMW) agents differed from patients with OA caused by high molecular weight (HMW) with regard to risk factors, asthma presentation and severity, and response to various diagnostic tests.


METHODS
Seventy-eight patients with OA diagnosed by positive specific inhalation challenge (SIC) were included. Anthropometric characteristics, atopic status, occupation, latency periods, asthma severity according to the Global Initiative for Asthma (GINA) control classification, lung function tests and SIC results were analysed.


RESULTS
OA was induced by an HMW agent in 23 patients (29%) and by an LMW agent in 55 (71%). A logistic regression analysis confirmed that patients with OA caused by LMW agents had a significantly higher risk of severity according to the GINA classification after adjusting for potential confounders (OR = 3.579, 95% CI 1.136-11.280; p = 0.029). During the SIC, most patients with OA caused by HMW agents presented an early reaction (82%), while in patients with OA caused by LMW agents the response was mainly late (73%) (p = 0.0001). Similarly, patients with OA caused by LMW agents experienced a greater degree of bronchial hyperresponsiveness, measured as the difference in the methacholine dose-response ratio (DRR) before and after SIC (1.77, range 0-16), compared with patients with OA caused by HMW agents (0.87, range 0-72), (p = 0.024).


CONCLUSIONS
OA caused by LMW agents may be more severe than that caused by HMW agents. The severity of the condition may be determined by the different mechanisms of action of these agents.
Servicio de Neumología, Hospital General Universitario Morales Messeguer, Murcia, Spain.
Olga
O
Meca
Servicio de Neumología, Hospital Universitario Vall d'Hebron, Barcelona, Catalonia, Spain.|Centro de Investigación en Red de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III (ISCIII), Barcelona, Spain.
María-Jesús
MJ
Cruz
Servicio de Neumología, Hospital Universitario Vall d'Hebron, Barcelona, Catalonia, Spain.|Centro de Investigación en Red de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III (ISCIII), Barcelona, Spain.
Mónica
M
Sánchez-Ortiz
Respiratory Department, Clinic University Hospital, Santiago de Compostela, Spain.
Francisco-Javier
FJ
González-Barcala
Servicio de Neumología, Hospital Universitario Vall d'Hebron, Barcelona, Catalonia, Spain.|Centro de Investigación en Red de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III (ISCIII), Barcelona, Spain.
Iñigo
I
Ojanguren
Servicio de Neumología, Hospital Universitario Vall d'Hebron, Barcelona, Catalonia, Spain.|Centro de Investigación en Red de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III (ISCIII), Barcelona, Spain.|Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Catalonia, Spain.
Xavier
X
Munoz
D000280:Administration, Inhalation; D000328:Adult; D000395:Air Pollutants, Occupational / Q000009:adverse effects*; D059366:Asthma, Occupational / Q000139:chemically induced* / Q000473:pathology*; D016535:Bronchial Hyperreactivity / Q000139:chemically induced / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D009784:Occupational Diseases / Q000139:chemically induced* / Q000473:pathology*; D016273:Occupational Exposure / Q000009:adverse effects*; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D055815:Young Adult
D000395:Air Pollutants, Occupational