Application of lot sampling of sputum AFB smears for the assessment of microscopy centres.
METHODS
Designated microscopy centres (DMC) and additional microscopy centres (AMC) performing sputum acid-fast bacilli (AFB) microscopy, the District TB Centre (DTC) and a reference laboratory (RL).


OBJECTIVE
To ascertain the feasibility of adopting lot sampling of AFB smears and to assess the performance of MCs employing Senior Tuberculosis Laboratory Supervisors (STLS) with no knowledge about the principles of quality assurance of AFB microscopy and RL-based laboratory technicians with training on quality assurance for blinded checking of AFB smears.


METHODS
Slides from MCs were transported to the DTC and the RL; 20 smears per month per MC were selected systematically; 1547 slides from DMCs and 726 from AMCs were checked, respectively, by STLSs at the DTC and by RL laboratory technicians. Discrepancies were resolved by referee.


RESULTS
The discrepancy between MC laboratory technicians and STLSs at the DTC was 4.7%, compared to 1% at the RL. The STLSs and RL-based laboratory technicians had 70 and 2 errors, respectively.


CONCLUSIONS
Lot sampling of AFB smears is feasible under field conditions. Assessment of MCs was more valid with RL-based technicians trained in principles of quality assurance of sputum AFB microscopy than with STLSs with no such training and working in the field.
Selvakumar
N
N
Tuberculosis Research Centre, Indian Council of Medical Research, Mayor V R Ramanathan Road, Chetput, Chennai 600 031, India. selvakumarn@hotmail.com
Prabhakaran
E
E
Murthy
B N
BN
Sivagamasundari
S
S
Vasanthan
S
S
Govindaraju
R
R
Perumal
M
M
Wares
F
F
Chauhan
L S
LS
Santha
T
T
Narayanan
P R
PR
D001431:Bacteriological Techniques; D005240:Feasibility Studies; D006801:Humans; D007753:Laboratories / Q000592:standards; D008853:Microscopy / Q000145:classification; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D011786:Quality Control; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000295:instrumentation*; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000382:microbiology