Page 192 - Registrar Orientation Manual 2016

Reference:
Effective date:
2015
Expiry date:
2018
Page:
18 of 28
Title: Laboratory Testing Guidelines (DRAFT)
Type:
Clinical Guideline
Version:
01
Authorising initials:
The DHB Shared Services Laboratory Test Referral Guidelines have this summary:
Specific investigations are not routinely required in the majority of patients with acute diarrhoea of up to 14 days duration. Enteric pathogens may not be amenable to treatment; however in some situations they pose a public health risk.
A laboratory diagnosis is useful for people who:
 may have an infection that could benefit from specific therapy;
 are at risk of severe complications e.g. intestinal failure and short bowel syndrome;
 are at risk of spreading infection; or
 are involved in an outbreak and may have a common source of infection.
Stool culture also has a role in selected patients with suspected IBD to exclude infectious causes. We recommend:
Do not send stool for culture in every admission with, or who develops, diarrhoea.
Do not send stool for culture unless there are good clinical indications.
Stool cultures have a low rate of pick up for identifying the likely pathogenic organism. The laboratory have establised a number of rules for stool testing:
 Only one faecal specimen a day will be processed.
 If diarrhoea develops after 3 days in hospital the laboratory will only test for C. difficile.
 Repeat testing of a patient who is positive for C.difficile toxin is not indicated within a 28
day period. A negative C.difficile toxin test may be repeated once if symptoms persist.
Further testing is not indicated during the same episode of diarrhoea.
 FOB testing is not performed on inpatients. Patients with symptoms or signs of
gastrointestinal bleeding require definitive investigations.
 Parasite examination has been limited to Giardia/Cryptosporidium. Full parasite work-up
will only be performed when clinical details indicate the patient has:
o recently travelled to countries with poor food or water services, o recently immigrated,
o eosinophilia with diarrhoea lasting more than 15 days ,
o immunocompromised status.
Swabs and other cultures ($34)
Swab cultures cost over $400,000 a year and respiratory swabs over $350,000.
We recommend:
Send material (fluid or tissue) if available for culture, not swabs.
Do not do send swabs for culture unless part of an accepted protocol (eg neutropaenic sepsis or throat infection) or if antibiotic therapy has failed.
Many swab results add little to patient management. The decisions to treat or not with antibiotics and with what antibiotic are made before swab cultures are available.
If available, material like pus or tissue (put in a urine container, without formalin!) rather than a swab should be sent for culture.
Nasal swabs are not informative for sinusitis and will not be cultured.
MRSA screen ($32)
MRSA screening costs over $200,000 a year. Please ensure it is indicated for infection control.