External quality assurance for the laboratory diagnosis of Buruli ulcer disease in Ghana.
OBJECTIVE
To assure the quality of the laboratory diagnosis of Buruli ulcer disease; microscopy and PCR were subjected to external quality assurance (EQA).


METHODS
Slides were read by test laboratory staff, followed by blinded re-reading by the controller. Parallel testing of PCR specimens was carried out at the local and external reference laboratory. Slides and PCR specimens with discordant results were subjected to a second reading/testing by the controller to determine the final result. For training purposes, slides and PCR specimens with discrepant results were subsequently re-read/re-tested under supervision at the test laboratory.


RESULTS
Microscopy. First reading: concordance rate 82.9%, discordance rate 17.1%, percentage false negatives 27.1% (sensitivity 72.9%), percentage false positives 10.1% (specificity 89.9%). Second reading: concordance rate 97.9%, discordance rate 2.1%, percentage false negatives 4.2% (sensitivity 95.8%), percentage false positives 0.6% (specificity 99.4%). PCR. First testing: concordance rate 87.9%, discordance rate 12.1%, percentage false negatives 8.2% (sensitivity 91.8%), percentage false positives 19.1% (specificity 80.9%). Second testing: concordance rate 96.2%, discordance rate 3.8%, percentage false negatives 4.7% (sensitivity 95.3%), percentage false-positives 2.1% (specificity 97.9%).


CONCLUSIONS
EQA identified deficiencies in the laboratory performance. Corrective action consisted in on-site training and reduced the number of false-negative and false-positive microscopy and PCR results.
Bretzel
G
G
Department of Infectious Diseases and Tropical Medicine, University of Munich, Munich, Germany. bretzel@lrz.uni-muenchen.de
Siegmund
V
V
Nitschke
J
J
Herbinger
K H
KH
Thompson
R
R
Fleischmann
E
E
Fleischer
B
B
Adjei
O
O
D019411:Clinical Laboratory Techniques / Q000592:standards*; D005188:False Negative Reactions; D005189:False Positive Reactions; D005869:Ghana / Q000453:epidemiology; D006801:Humans; D016013:Likelihood Functions; D008853:Microscopy / Q000379:methods / Q000592:standards; D009165:Mycobacterium Infections, Nontuberculous / Q000175:diagnosis* / Q000453:epidemiology; D019911:Mycobacterium ulcerans / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000379:methods / Q000592:standards; D011237:Predictive Value of Tests; D011786:Quality Control; D012680:Sensitivity and Specificity