Using Multiple Diagnostic Methods for Occupational Asthma Assessment

Occupational asthma (OA) is a significant work-related respiratory disorder requiring accurate diagnostic methods. This study evaluates the sensitivity and specificity of PC20 variability in OA diagnosis and compares it with peak expiratory flow rate (PEFR) monitoring.

A retrospective descriptive study was conducted. Fifty-one individuals with suspected OA were assessed. Pulmonary function tests, PEFR monitoring, and methacholine challenge test were performed. PC20 variability was analyzed by comparing values during workplace exposure and after exposure cessation.

A total of 51 suspected occupational asthma (OA) cases were evaluated (mean age: 38.14 ± 8.10 years, 68.6% male). The most common symptom was shortness of breath (mean duration: 19.61 ± 29.23 months), with an average occupational exposure of 7.34 ± 6.82 years, primarily to low molecular weight (LMW) agents. OA was diagnosed in 70.6% (n = 36) of cases, with longer symptom duration and exposure time than nonoccupational asthma. OA cases had longer symptom duration (22.50 ± 32.98 months vs. 12.67 ± 16.08 months in non-OA cases) and slightly longer occupational exposure (7.51 ± 5.94 years vs. 6.92 ± 8.83 years). PC20 (provocative concentration of methacholine causing a 20% fall in FEV₁) variability was analyzed. IgE-mediated asthma was found in 16.7% of LMW-exposed cases, whereas nonimmunologic mechanisms accounted for 83.3%. PC20 levels were lower during exposure but improved after exposure cessation. PC20 variability was positive in 77.8% (n:28) of cases and had a sensitivity of 90% and a specificity of 92%. In 13.9% of OA cases, methacholine challenge test could not be performed due to low FEV1 levels, and diagnoses were made based on PEFR variability. If PC20 variability was not performed, PEFR variability alone could lead to misclassification in 22.2% (n:8) of cases. The majority of OA cases were associated with the metal, foundry, and ceramics industries, with inorganic dust exposure as the most common exposure (27.8%).

PC20 variability is a highly sensitive and specific tool for diagnosing OA and may help reduce misdiagnosis associated with PEFR-based assessments. However, in patients where the methacholine challenge test is not feasible, PEFR variability remains a valuable alternative for diagnostic evaluation. Integrating PC20 variability into diagnostic protocols can enhance accuracy and improve patient management.