Precipitins and specific IgG antibody to Aspergillus fumigatus in a chest unit population

The enzyme linked immunosorbent assay (ELISA) for detecting IgG antibodies to Aspergillus fumigatus is more sensitive than the measurement of Aspergillus precipitins. The relation of the results from both techniques to the clinical pattern of disease in a large unselected group of patients from a large referral centre is unknown.

The clinical relation of precipitins to Aspergillus fumigatus to clinical disease was determined retrospectively in 98 patients attending a primary referral centre. Precipitin results were compared with the specific IgG antibody to A fumigatus in 88 of the sera. Precipitins were determined by the agar gel double diffusion test and specific IgG antibody to A fumigatus by a quantitative ELISA.

Precipitins were detected in the unconcentrated serum of 51 patients. Thirty nine of these had a mycetoma or allergic bronchopulmonary aspergillosis, 34 having specific IgG antibody to A fumigatus more than the control range. Forty seven patients had precipitins only after threefold concentration of serum or to only one of the four A fumigatus antigen extracts. Most of these had specific IgG in or near the control range. Thirty of these had A fumigatus skin test negative asthma or bronchiectasis, in which aspergillus was probably not pathogenic. There was a close relation between the level of antibody detected by the ELISA and the number of precipitin lines.

This study reaffirmed the supportive role of aspergillus precipitins in the diagnosis of pulmonary aspergillosis. No additional benefit in the routine use of the ELISA was seen. It also showed that care should be taken in interpreting positive precipitin results from concentrated serum and that using several rather than one A fumigatus antigen extract is helpful for identifying allergic aspergillosis.