Quality assurance studies in eight State tuberculosis laboratories in India.

SETTING

Tuberculosis Research Centre, Chennai, India.

OBJECTIVE

To undertake quality assurance studies in sputum smear microscopy at eight State-level laboratories in India using a panel of stained smears.

DESIGN

Coded panels of stained smears (100 slides in rounds I-IV and 50 slides in Round V), comprising different grades of positivity, were sent to each centre at 6-monthly intervals. The results obtained were analysed for consistency of positive and negative results and overall agreement, as well as discordance.

RESULTS

Consistency of positives ranged from 38% to 100%, indicating under-reading at some sites. The negative consistency was better, however, with only five of the total of 95 readers in all rounds yielding a consistency of less than 100%. Considering overall agreement, seven of the eight centres showed an agreement of over 90%. Four of the eight centres gave no false-positive result. For the remaining centres the false positivity rate varied from 2% to 7%. A wide variation was also observed in the proportion of false-negatives (3%-52%).

CONCLUSIONS

This study helped in the evaluation of the performance of individual laboratories and in identifying the drawbacks of this system of proficiency testing.