Use of an Enzyme-Linked Immunosorbent Assay Technique in the Differential Diagnosis of Active Pulmonary Tuberculosis in Humans

Sera from patients with active pulmonary tuberculosis and pulmonary diseases frequently mimicking tuberculosis were assayed for immunoglobulin G antibody activity to purified protein derivative (PPD) by an enzyme-linked immunosorbent assay. A method of standardization was developed to limit assay variation. Patients with active pulmonary tuberculosis had a significantly greater mean level of antibody than had patients with atypical tuberculosis (P = 0.005), sarcoidosis (P = 0.0001), histoplasmosis (P = 0.004), blastomycosis (P = 0.008), or cryptococcosis (P = 0.017), patients who had received bacille Calmette-Guerin vaccination (P = 0.003) or who had a history of treated tuberculosis (P = 0.003), and PPD skin test-positive and skin test-negative control subjects (P = 0.001). This technique may have potential use as a rapid diagnostic aid in evaluating patients with suspected active pulmonary tuberculosis. The incidence of disease caused by Mycobacterium tuberculosis has steadily declined over the past several decades; currently 30,000 new cases are reported annually in the United States, and almost 3,000 deaths occur. The most recently available data suggest this previously downward trend has