How do I diagnose?

How do I diagnose?

This section contains the recommended approach at our laboratory to testing for different infections. The search function in the page header can also be used to find topics in this section.

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Special topics

Congenital and Perinatal Infection
A note on TORCH testing

TORCH = Toxoplasmosis, Other (e.g. Parvovirus, Syphilis), Rubella, CMV, HSV

Whilst the term “TORCH” can be useful for remembering important infectious causes of congenital infection, its use in the laboratory/diagnostic setting is now discouraged, to the point where our laboratory no longer accepts requests for “TORCH testing”. The reasons for this include:

  • It is a non-specific term, and promotes a ‘shotgun’ approach to diagnosis. Given that congenital infections are rare (i.e. low pre-test probability) any positive results generated from this approach are more likely to be false positives, rather than true positives.
    • This can lead to further investigations, which may be unnecessary, and sometimes invasive.
  • Rubella is no longer present in NZ (and many other developed countries) so is no longer seen as a cause of congenital infection unless contracted overseas in an unvaccinated woman.
  • HSV almost never causes congenital infection as such, it is more important in the early postnatal setting.
  • Some congenital infections cause specific syndromes, e.g. Parvovirus and hydrops fetalis, that can usually be differentiated from others on USS, so warrant targeted testing.