Against the proposition: for the diagnosis of viral infections, commercial assays provide more reliable results than do in-house assays.

There are no differences inherent in the design of commercial or in-house assays and their early development is similar. The same principles apply and it is on the same criteria of accuracy, reproducibility and clinical relevance of results that all assays are judged. However, if there is sufficient uptake of a commercial assay, its strengths and any flaws soon become apparent and it will only be the best commercial assays that remain in the market. For the in-house assays it is through comparability studies and external quality assessment (EQA) schemes that the best can be demonstrated, albeit this information is only accessible initially to the EQA provider and the laboratories using the assays. The EQA results described here support my supposition that, for the diagnosis of viral infections, commercial assays do not provide more reliable results than do in-house assays.