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Quality assurance studies in eight State tuberculosis laboratories in India
C N Paramasivan1, P Venkataraman, J S Vasanthan
1Tuberculosis Research Centre, Chennai, Tamil Nadu, India. sivamparam@hotmail.com
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.