Culture Conversion Rate at 2 Months of Treatment According to Diagnostic Methods among Patients with Culture-Positive Pulmonary Tuberculosis

Abstract

IntroductionThe culture-negative conversion rate of sputum after 2 months of treatment in patients with pulmonary tuberculosis (TB) is used as a reliable surrogate marker for relapse after completion of treatment. We hypothesized that culture conversion of sputum at 2 months of anti-TB treatment and the time to culture conversion are different among pulmonary TB patients who are diagnosed using different methods.MethodsCulture-confirmed pulmonary TB patients who were diagnosed between 1 January, 2011 and 31 December, 2012 were classified into three groups based on the diagnostic method that prompted treatment initiation: positive acid-fast bacilli (AFB) staining of sputum (smear-positive group), negative AFB staining, but Mycobacterium tuberculosis was cultured from sputum (culture-positive group), and positive AFB staining, positive polymerase chain reaction (PCR) for M. tuberculosis, or culture of M. tuberculosis from a bronchoscopic specimen (bronchoscopy group). Rates of negative mycobacterial culture conversion at 2 months of anti-TB treatment and the time to negative culture conversion of sputum were compared among the three groups.ResultsA total of 203 patients with culture-confirmed pulmonary TB were included in the final analysis. TB patients in the culture-positive group (94.1%) and the bronchoscopy group (97.6%) showed a higher culture conversion rate at 2 months of treatment than those in the smear-positive group (78.7%, P = 0.001). Additionally, the time to culture conversion was longer in the smear-positive group (median, 40 days) than in the culture-positive (median, 19 days; P = 0.009) and bronchoscopy groups (median, 29 days; P = 0.004).ConclusionsThe higher culture conversion rate at 2 months and the shorter time to culture conversion among pulmonary TB patients with a negative AFB smear suggests the feasibility of shortening treatment duration and isolation in these patients.

Time to sputum culture conversion and its determinants among Multi-drug resistant Tuberculosis patients at public hospitals of the Amhara Regional State: A multicenter retrospective follow up study

“…In MDR-TB patients smear +2 and +3 resulted in delayed culture conversion time. This finding is in line with that of a study conducted in Latvia [ 21 ], Korea [ 22 ], and Indonesia [ 23 ]. Patients with high smear grading had high bacillary load.…”

“…Having a high bacillary burden suggests a stronger infectivity and requires a longer isolation period and a more intensive treatment. Thus, it needs time to clear the bacilli if the bacillary load is high [ 22 ]. The second possible explanation could be that the presence of a high bacillary load is better associated with a reduction in bacterial killing and sterilizing activity of anti-TB drugs.…”

Smear grading and the Mantoux skin test can be used to predict sputum smear conversion in patients suffering from tuberculosis

“…Conversely, smoking was shown to be associated with sputum smear conversion after 2 months of anti-tuberculosis treatment [ 30 ]. Patients with cavitary lesions have demonstrated a higher rate of non-conversion [ 31 ], [ 32 ], although this association was not statistically significant in the present study. A possible bias due to chest radiograph interpretation may be the reason for such a finding.…”

Changes in Diagnostic Methods for Pulmonary Tuberculosis between 2005 and 2013

“…Recent studies illustrate the benefits of bronchoscopy as a diagnostic method in patients with possible pulmonary TB 12 13 . According to one of our recent studies, TB patients diagnosed using bronchoscopy exhibit higher culture conversion rates at 2 months and reduced time to culture conversion compared with other patients 14 . In this context, increased use of bronchoscopy to diagnose TB could have a positive impact on prognosis and disease transmission.…”