Oversensitive faecal PCR tests causing distress

A new assay technique may be picking up harmless parasites, and causing unnecessary treatment and anxiety

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The introduction of a newer and more sensitive assay technique may be picking up harmless parasites, and causing unnecessary treatment and anxiety, experts warn

The Australasian Society for Infectious Diseases (ASID) has now added its voice to the growing concern over results from a PCR technique introduced into laboratories around the country from 2013.

“Whilst we welcome the recent adoption of molecular testing for gastrointestinal bacterial and parasitic pathogens, we have significant concerns regarding the parasites in the multiplex PCR for children and their families,” said ASID president, Professor Cheryl Jones.

“We therefore urge clinicians not to investigate or treat for faecal pathogens in the absence of diarrhoea or other gastro-intestinal symptoms,” said Professor Cheryl Jones.

Two out of the five parasites included in the panels, Dientamoeba fragilis and Blastocystis spp., have uncertain clinical significance and are very likely non-pathogenic, said Dr Asha Bowen, Perth paediatric infectious diseases specialist and lead author of ASID’s report.

The quick new test has seen prevalence rates of D. fragilis and Blastocystis rise to around 17% of all stool samples, predominantly in children under 10 years.

In an open letter, the paediatric infectious diseases physicians of ASID said they have been fielding a growing number of queries from concerned parents and GPs confused about the interpretation of the results.

Increased reporting of D. fragilis and Blastocystis has led to unnecessary antimicrobial use, as their role as gastrointestinal pathogens is “controversial and unproven”, according to Dr Bowen and her colleagues.

To prevent over-testing and overtreatment, authors of the ASID report also recommend that clinicians avoid specific treatment and further testing for D. fragilis and Blastocystis.

This new statement from ASID strengthens warnings issued by the Royal College of Pathologists of Australasia in late 2015, which recommended laboratories don’t include tests for these two pathogens in their enteric multiplex PCRs.

“Ignoring the result in the absence of symptoms and providing the patient with reassurance is probably most helpful,” said ASID member Dr Bowen.

MJA 2016; online 18 April