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External quality assessment of cytomegalovirus DNA detection on dried blood spots

DOI: 10.1186/1471-2180-8-2

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The 27 responding laboratories from 14 countries submitted 33 datasets obtained by means of conventional PCR (n = 5) or real-time PCR (n = 28) technologies. A correct positive result was reported in at least 91% of datasets in samples with a viral load of 8.8 × 104 copies/ml or higher. However only 59% and 12% identified the 9.4 × 103 and 7.3 × 102 copies/ml samples, respectively, correctly as positive. False positive results were reported by 9% of laboratories and in 11% of datasets.These results indicate a clear need for improvement of methods as sensitivity and false-positivity still appear to be a major problem in a considerable number of laboratories.Congenital CMV infection is the most widespread congenital infection in humans and is a major cause of neurological damages such as hearing loss, visual impairment and mental retardation in children. Diagnosis of congenital CMV infection requires laboratory testing done on samples collected in the first three weeks of life. Testing for CMV-DNA in neonatal blood collected on filter-paper (dried blood spot, DBS) has proved a valid means of diagnosis with both clinical and epidemiological relevance. Applications of this assay range from diagnosis in the neonatal period as an alternative to the conventional urine culture method to the unique quality of ascertaining whether damages arising during infancy are due to congenital infection [1,2].Most laboratories use an in-house developed assay for detection of CMV-DNA in DBS. However, no international standard is available and previous external quality assessment studies have shown that the quality of nucleic acid amplification methods such as PCR varies considerably between laboratories [3,4]. Therefore a quality assessment study for the detection of CMV-DNA on DBS was recommended by the European Congenital CMV Initiative (ECCI) group and was organised by QCMD (Quality Control for Molecular Diagnostics). We report the results of the CMV-DNA amplification assays performed


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