Laboratory investigation of infectious diarrhoea
In March 2008, bpacnz produced a report on the laboratory investigation of infectious diarrhoea which included five key recommendations:
- Laboratory investigations are not routine for people with infectious diarrhoea
- Testing for giardia and cryptosporidium should only be requested if there are risk factors
- Testing for ova and cysts is rarely indicated
- If laboratory testing is indicated, faecal culture is the first-line test
- When faecal culture testing is requested, a single stool sample should be tested
This report will discuss how testing behaviour in New Zealand has changed over the past five years and includes feedback on the testing requested by all New Zealand health providers for patients registered to your practice in 2011.
The five recommendations for the laboratory investigation of infectious diarrhoea in New Zealand
Laboratory investigations are not routinely required for most people with acute diarrhoea
Approximately 20% of people with an acute gastrointestinal illness will visit their general practitioner. If the person has no known risk factors, such as age under five years or over 70 years, has bloody stool or is a food handler,1 laboratory testing is not indicated. Management involves adequate rest and maintaining hydration status.
Tests for giardia and cryptosporidium should only be requested if there are risk factors
Testing giardia and cryptosporidium is indicated only when a person has diarrhoea for longer than seven days, recent attendance at a childcare centre, is immunocompromised or following overseas travel.
Testing for ova and cysts is rarely indicated
Testing for ova and cysts is appropriate for people with diarrhoea who have recently travelled to countries with poor food or water sources, recently immigrated, are immunocompromised or have persistent diarrhoea with esoinophilia.
Over the past five years, the number of tests for infectious diarrhoea has decreased across the three tests bpacnz monitored using data from the Ministry of Health National Collections.2,3,* It shows that in 2011, there were 32% fewer faecal culture and ova and cysts tests ordered, and 27% fewer giardia tests ordered than in 2007.
If laboratory investigation is indicated, faecal culture is the first-line test
When testing is indicated, a stepwise approach should be taken. Faecal culture should be the initial test. Other tests should be requested only when there are additional risk factors or symptoms persist for more than two weeks.
When faecal culture testing is requested, a single stool specimen should be tested
Historically, General Practitioners were encouraged to request a series of faecal culture tests e.g. "faecal culture ×3". This practice is no longer recommended as analysis of laboratory testing has shown that the vast majority of positive tests are identified on the first specimen.1 Therefore, a single sample is required initially with further specimens only if symptoms persist and the initial specimen is negative.
The percentage of occasions where a single faecal culture test was requested as the initial test for infectious diarrhoea† in New Zealand increased from 33% in 2007 to 38% in 2011. There is still room for improvement.
Report for Sample Medical Centre
Tests for your registered patients could be ordered by any New Zealand health provider. Does the number of tests for your patients in 2011 align with what you would expect based on the number of general practitioners working in your practice?
|Faecal culture tests requested for your patients||25||Percent of occasions that a single faecal culture test was requested for your patients in 2011 as the initial test for infectious diarrhoea†|
|Giardia/cryptosporidium tests requested for your patients||10|
|Ova and cysts tests requested for your patients||5|
|Health providers who ordered tests for your patients||5|