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Testing for enteric pathogens
Follow up report

This report is a follow-up to the Testing for Enteric Pathogens Report published in March 2008. This report was produced because of apparent over testing for enteric pathogens in primary care. Nationally there have been significant changes to the pattern of testing. These changes are outlined below along with your data, allowing you to compare changes in your pattern of testing with those of your peers.

1. Ordering of Faecal Culture Tests

There has been a significant decrease in the volume of faecal culture tests ordered by general practitioners since 2007 (prior to the original report). This change is consistent with the advice that laboratory investigations are not required in most people with acute diarrhoea.

Figure 1: Faecal culture test ordering
Faecal culture test ordering

Ordering of faecal culture as a seriesContributing to the decrease in faecal cultures has been a reduction in the number of faecal cultures ordered as part of a series*. Although they have reduced from approximately one-half to one-third of all requests, this still seems high given that this practice is rarely necessary.

Nationally, in 2007 54% of the faecal cultures requested were part of a series, by 2009 33% of thefaecal cultures requested nationally were part of a series.

Analysis of laboratory testing has shown that the vast majority of positive tests are identified on the first specimen. Therefore, a single sample is required initially, with further specimens only if symptoms persist and the initial specimen is negative.

Notes:
*series is defined as more than one specimen for the same patient and same doctor, which occurs within 14 days of the first specimen. Data for this section have been excluded where the NHI number was not recorded.
Data is assigned to you based on the recorded NZMC number for requested tests. Data has been excluded where the NZMC number was not recorded.

Time periods:  2007 is defined as 1 January 2007 - 31 December 2007.
  2009 is defined as 1 November 2008 - 31 October 2009.

2. Testing for Ova and Cysts

The most common causes of parasitic diarrhoea in New Zealand for people who have not travelled, are giardia and cryptosporidium. Diarrhoea caused by other parasites is uncommon, therefore testing for ova and cysts is rarely indicated.

Figure 2: Ova and cyst test ordering
Ova and cyst test ordering

3. Testing for Giardia and Cryptosporidium

There are limited indications for testing for giardia and cryptosporidium. Testing is only indicated when a person has diarrhoea:

  • For longer than 7 days
  • Following recent overseas travel, tramping trip or drinking from springs/rivers
  • Following attendance at childcare centre
  • Is immunocompromised

Cryptosporidium is also associated with lambs and calves, and there are occasionally outbreaks in swimming pools.

Figure 3: Giardia/cryptosporidium test ordering
Ova and cyst test ordering