Evaluation of the clinical utility of reflex GMS and AFB stains on BAL specimens from lung transplant patients

Abstract

Bronchoalveolar lavage (BAL) has a useful role in the detection of infectious diseases. Grocott methenamine silver (GMS) and acid-fast bacilli (AFB) are ancillary stains that aid in the cytologic detection of fungal and mycobacterial organisms. However, the utility of these stains in conjunction with microbiological testing is unclear. BAL specimens from lung transplant patients between January 1, 2018, to December 31, 2018, were evaluated. Inclusion criteria included cases with both GMS and AFB stains and concurrent fungal and mycobacterial microbiology testing. The staining findings were correlated with concurrent microbiology findings, including cultures and immunofluorescent smears. A total of 231 BAL specimens were identified. GMS stain was positive in 19.5% and AFB in 1.3%. Fungal microbiology was positive in 23.4% and mycobacterial microbiology in 6.1%. A total of 87.9% of cases had concordant findings between cytology stains and microbiology tests and 12.1% had discrepant findings. Notably of the discrepancies, 3.0% had positive GMS and negative fungal microbiology and 6.9% had positive fungal microbiology and negative GMS. No cases had positive AFB with negative mycobacterial microbiology whereas 4.8% had positive mycobacterial microbiology and negative AFB stain. We show that staining for AFB on BAL material in lung transplant patients had limited benefit when concurrent microbiology was performed. GMS staining shows a small benefit. We recommend reflex testing for fungal organisms but not mycobacterial organisms in lung transplant patients.