Page 188 - Registrar Orientation Manual 2016

Reference:
Effective date:
2015
Expiry date:
2018
Page:
14 of 28
Title: Laboratory Testing Guidelines (DRAFT)
Type:
Clinical Guideline
Version:
01
Authorising initials:
Faecal Calprotectin ($105)
Calprotectin tests cost over $300,000 a year. We have now restricted testing to SMO requests. The laboratory will not repeat calprotectin testing within 28 days.
The DHB Shared Services Laboratory Test Referral Guidelines have the following:
Faecal calprotectin is a marker of intestinal mucosal inflammation that can be useful in differentiating between irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) in symptomatic patients. In IBD, levels correlate with disease activity and a concentration <50 μg/g is considered to be a good negative predictor (published negative predictive values 70-90%) and to help triage patients for colonoscopy. Levels >50 μg/g are associated with a risk of relapse.
The guidelines note the following indications and referral criteria:
 In patients presenting with diarrhoea, first line tests to exclude pathology may include CBC, CRP, ferritin, TFTs, stool culture and ova and parasites if travel history.
 Faecal calprotectin is a second line investigation if there is a concern about possible IBD, although may be a first line investigation if there is a family history of IBD. It may be particularly helpful in paediatric IBD when other investigations may be normal.
 In the presence of “red flags” (e.g. unexplained iron deficiency anaemia, rectal bleeding, weight loss or family history of colon cancer), faecal calprotectin testing may incur unnecessary delay in referral to a gastroenterologist and especially where there is likely consideration for colonoscopy.
Free light chains ($52)
Free light chain testing costs over $120,000 a year. The test measures the total amount of immunoglobulin light chain in the serum that is unbound (“free”) to immunoglobulin heavy chains. An imbalance of kappa v lambda isotypes is suggestive of monoclonal plasma cell dyscrasia.
The test can be used instead of urinary Bence Jones Protein in screening and diagnosis.
The DHB Shared Services Laboratory Test Referral Guidelines have the following:
The International Myeloma Working Group guidelines suggest that Serum Free Light Chains are used for prognostic purposes in patients with monoclonal gammopathy of unknown significance (MGUS) and also smouldering multiple myeloma, active multiple myeloma and amyloidosis.
The test is indicated if the patient:
 has known or suspected myeloma or MGUS
 has known or suspected amyloidosis
 has unexplained renal impairment or proteinuria
 has unexplained peripheral neuropathy
Should only be performed with a maximal frequency of once every 4 weeks. It is anticipated testing is needed no more frequently than every 3 months unless on active chemotherapy.
Our multiple myeloma guidelines suggest the acronym CRAB is a helpful guide to investigation for myeloma. Test if any of the following are unexplained:
Calcium elevation
Renal impairment (acute or chronic)
Anaemia (normochromic, normocytic < 100g/L or > 20g/L below normal) Bone (lytic lesion, crush fractures, osteopenia)