Kh. Engler et al., International external quality assessment scheme for the laboratory diagnosis of diphtheria, J MED MICRO, 50(11), 2001, pp. 1006-1012
An international external quality assessment (EQA) scheme has been establis
hed so as to evaluate the proficiency of specialist, national diphtheria re
ference laboratories in the laboratory diagnosis of diphtheria. Six simulat
ed clinical specimens were freeze-dried and distributed to 23 participants
in 20 countries. Participants were asked to isolate, identify and perform t
oxigenicity, testing on any corynebacteria present and to complete a simple
questionnaire describing the procedures and reagents used. Only three labo
ratories obtained correct biochemical and toxigenicity, results for all six
specimens. The majority of laboratories performed better with toxigenicity
testing than with the biochemical identification. Of concern were the resu
lts from three laboratories that failed to isolate any corynebacteria from
four or more of the specimens. In one centre this was shown to be due to la
ck of availability of 'in-date' media and, in the other two, was presumed t
o be due to lack of experience in primary laboratory diagnostics for this o
rganism. It is essential that countries, globally, maintain awareness and l
aboratory capabilities in this specialised area of microbiology. EQA is an
invaluable process, which enables laboratories to monitor, evaluate and imp
rove their own performance in such areas.