Random blinded rechecking of AFB smears in a pilot project at an intermediate reference laboratory.

BACKGROUND: In most developing countries, sputum smear microscopy for acid-fast bacilli remains the front line and often the only diagnostic tool for the diagnosis of tuberculosis (TB), making quality assurance of smear microscopy an important activity. OBJECTIVE: To evaluate the results of a pilot study, where the random blinded rechecking for the entire state of Delhi was conducted at a reference laboratory. METHODOLOGY: Slides from 25 Revised National Tuberculosis Control Programme designated districts (200 peripheral microscopy centres) in Delhi were re-read after proper coding by all the Senior Tuberculosis Laboratory Supervisors (STLS) at an intermediate reference laboratory under proper supervision. RESULTS: Of 12,162 re-read slides, 204 discrepant results were found. Of these, 150 (73.5%) errors were attributed to the peripheral microscopy centres and 54 (26.5%) to STLS. High false-positive errors were observed at a frequency of 12/150 (8%), and high false-negative errors at a frequency of 38/150 (25%). Minor errors, i.e., low false-negative, low false-positive and quantification errors, were observed at frequencies of respectively 68/150 (45.3%), 17/150 (11.3%) and 15/150 (10.0%). CONCLUSION: Greater stringency in the supervision of random blinded rechecking at the district level is essential to make smear rechecking more efficient and effective.

Phylogenetic associations with drug-resistant Mycobacterium tuberculosis isolates in a paediatric population.

SETTING: Department of Microbiology, National Institute of Tuberculosis and Respiratory Diseases, New Delhi, India. OBJECTIVES: As paediatric tuberculosis (TB) is a surrogate marker for actively transmitted disease in a community, we investigated drug resistance patterns of 97 Mycobacterium tuberculosis complex strains isolated from children and explored their phylogenetic associations. DESIGN: A total of 111 paediatric patients who attended the out-patient department during the study period 2009-2011 and whose sputum samples were sent to the Microbiology Department for liquid culture and drug susceptibility testing (DST) were included in this study. DST and spoligotyping were performed on cultures positive for M. tuberculosis complex. RESULTS: DST against four first-line drugs showed that 31 of 97 (32%) strains were pan-susceptible, while 66/97 (68%) were resistant to at least one drug, including 55/97 (56.7%) that were resistant to at least isoniazid and rifampicin (i.e., multidrug-resistant). The majority of the isolates (n = 81/90, 90%) belonged to the principal genetic group 1 strains, the most predominant spoligotyping clusters being spoligotyping international type (SIT)1/Beijing (n = 28), SIT26/CAS1-Delhi (n = 27) and SIT53/T1 (n = 6). CONCLUSION: The involvement of Beijing and CAS1-Delhi clades in paediatric TB patients suggests that these two lineages play a major role in ongoing active transmission.