Application of acid-fast staining combined with GeneXpert MTB/RIF in the diagnosis of non-tuberculous mycobacteria pulmonary disease

Abstract

Objective: To evaluate the clinical diagnostic value of positive acid-fast staining combined with negative GeneXpert MTB/RIF in the diagnosis of non-tuberculous mycobacteria pulmonary disease (NTM-PD).

Methods: A total of 133 inpatients with confirmed NTM-PD were included consecutively between January 1, 2018 and December 31, 2019, at Tongji Hospital and Jinyintan Hospital, Tongji Medical College of Huazhong University of Science and Technology, in Wuhan, China. One hundred patients with confirmed pulmonary tuberculosis (PTB) were randomly included as the control group.

Results: The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of positive acid-fast staining combined with a negative GeneXpert MTB/RIF result were 51.13% (95% confidence interval (CI) 42.52-59.73%), 97.00% (95% CI 93.60-100.40%), 95.78% (95% CI 90.98-100.57%), and 59.88% (95% CI 52.25-67.51%), respectively. When subjects were limited to patients with positive acid-fast staining, the sensitivity of a negative GeneXpert MTB/RIF result was 88.31% (95% CI 80.97-95.65%). When acid-fast staining was conducted ≥3 times, the sensitivity of this combination diagnosis method increased to 61.67% (95% CI 49.00-74.33%).

Conclusions: Positive acid-fast staining combined with a negative GeneXpert MTB/RIF result could be an effective and time-saving method for the diagnosis of NTM-PD.

Keywords: Acid-fast staining; Diagnosis; GeneXpert MTB/RIF; Non-tuberculous mycobacteria; Pulmonary tuberculosis.