Beryllium Lymphocyte Proliferation Test: Differential Diagnosis of Sarcoidosis and Chronic Beryllium Disease.

Background: Chronic beryllium disease (CBD) is considered a phenocopy of sarcoidosis, generally caused by occupational exposure to beryllium. Its diagnosis relies on the demonstration of beryllium sensitisation by the beryllium lymphocyte proliferation test (BeLPT).

Research question: How well does the BeLPT discriminate between CBD and sarcoidosis in patients with suspected beryllium exposure and what are the clinical characteristics of these two groups?

Study design and methods: BeLPT results and clinical characteristics of patients with suspected beryllium exposure were retrospectively analysed.

Results: A total of 1,234 BeLPTs from 431 patients were included. Of 210 patients with established granulomatous disease, 87 patients (41.4%) were diagnosed with CBD and 106 (50.5%) with sarcoidosis; in 17 cases (8.1%) the BeLPT results were inconclusive. The remaining 221 patients had other diagnoses or could not be classified. A single BeLPT had a sensitivity of 61.5% (CI 55.8-67.0) and a specificity of 90.8% (86.5-93.9). For split-sample tests, the sensitivity and specificity were 76.0% (67.7-82.8) and 80.4% (71.4-87.1), respectively. Patients with CBD had lower lung function than those with sarcoidosis, as measured by forced vital capacity (mean z-score -1.58 vs -0.75; p = 0.002). A restrictive pattern was more common in CBD than in sarcoidosis (41.0% vs 14.8%; OR = 3.99; p = 0.002).

Interpretation: Despite low sensitivity, the BeLPT was able to detect CBD in 41.4% of patients with a granulomatous disease and suspected beryllium exposure. CBD was associated with lower lung function compared with sarcoidosis.