SW & Wessex Regional Audit Laboratory Investigations of Chronic Diarrhoea Sue Bird. Clinical Pathology, Dorset County Hospital, DORCHESTER, Dorset Introduction Results The British Society of Gastroenterology (BSG) recently published guidelines for the investigation of chronic diarrhoea (1). The BSG graded the strength of their recommendations A, B or C according to the category of evidence. These are shown next to the recommendation and are as follows:-A – Requires evidence from at least one randomised controlled trial or a meta-analysis of randomised controlled trials.B – Requires evidence from prospective, retrospective or cross sectional clinical studies without randomisation.C – Evidence based on expert reports or opinion in the absence of directly applicable studies of good quality. Methods A set of 8 standards thought to be appropriate for biochemistry laboratories was developed from the recommendations. A questionnaire was sent to 21 laboratories in the South West and Wessex Regions via the audit leads for the two regions. Standard and BSG Recommendation % Detail from audit results 1. Suitable serological tests for screening for coeliac disease should be available. Coeliac disease is the most common small bowel enteropathy in Western populations. Patients with diarrhoea should be screened for this using serological tests (currently antiendomysium antibodies) which have a high sensitivity and specificity for the disease (A) st line test :-anti-tissue transglutaminase Abs – 15 labs, anti-endomysial Abs – 1 lab Anti-gliadin Abs – 1 lab. Workload: 636 to 13,316* tests/year (*includes other labs). 7 routinely screened for IgA deficiency, if deficient 6 did IgG Abs 13 labs added comments to results : 7 labs gave false neg warnings re. gluten-free diets/IgA def., 6 labs suggested GI referral when appropriate. 2. Screening tests for laxative abuse should be available. Factitious diarrhoea becomes increasingly common in specialist referral practice, and screening for laxative abuse should be performed early in the course of investigation (B). 100 All labs < 30 samples /year, 6 labs < 3 samples/year. Only 1 lab in the survey performed testing in its own lab (using tlc). The other labs sent samples away, using 6 different labs outside the SW & Wessex regions. 3. Laboratories should discourage the three-day faecal fat test. Quantification of three-day faecal fat is poorly reproducible, unpleasant and non-diagnostic and its use should be discouraged (C). 88 One lab samples/year. One lab 6 samples/year. A third lab had assayed one sample in a paediatric patient with cystic fibrosis (faecal elastase estimation not appropriate). 4. Other alternative tests to the three-day faecal fat analysis should be available. Single stool analyses such as faecal fat concentration and semi-quantitative methods such as acid steatocrit correlate moderately well with three day faecal fat quantification and offer an alternative method of assessing fat malabsorption but are not readily available in most centres. Newer specific tests of pancreatic dysfunction, such as stool elastase are preferred ( B). 100 All 17 labs offered faecal elastase test. 1 lab measured 1-day faecal fat conc. (30 tests/year). No labs performed acid steatocrits. 13/17 hospitals offered stool fat microscopy (2 for paediatric patients only). No labs involved in breath tests for fat malabsorption (1 aware done by med physics). 5. Laboratories should discourage urine or serum D-xylose tests. Non-invasive investigations for small bowel enteropathy such as urine or serum D-xylose testing, although of high sensitivity in clinical studies, often have a poor performance in routine practice and have largely been superseded by the availability of small bowel histology. Their use is not encouraged (C) lab offered urine or serum D-xylose but none had been requested since Laboratories should offer faecal elastase assays. Non-invasive pancreatic function tests include urine tests such as the Pancreolaural test and stool tests such as faecal elastase or chymotrypsin. They depend on a significant loss of exocrine function and thus are only reliable in moderate / severe pancreatic disease, with poor sensitivity for mild disease. Non-invasive tests have approximately equivalent sensitivities for the detection of pancreatic insufficiency (B). Faecal elastase offers the advantages of acceptable reliability and convenience (a single stool is required ) without the need for prolonged urine collections, and is therefore recommended as the test of first choice in patients who present with diarrhoea of putative pancreatic origin (C). 100 Other tests of pancreatic function offered : Faecal chymotrypsin – 1 lab (<10/year). Faecal lipase - 0 labs. Urine NBTP/PABA – 1 lab (<10/year). Urine Pancreolauryl – 8 labs (3 labs - <10/year; 3 labs 10-50/year; 2 labs /year). Faecal Tryptic activity – 1 lab (<10/year). 7. Glucose hydrogen breath tests should be available. Culture of small bowel aspirates is the most sensitive test for small bowel bacterial overgrowth (SBBO) but methods are poorly standardised and positive results may not reflect clinically significant SBBO (B). Hydrogen breath tests have poor sensitivity but acceptable specificity, and are of value when a positive result is obtained. The glucose hydrogen breath test is recommended (B). 24 Only 1 lab was involved in the glucose hydrogen breath test. 3 labs were aware that testing was carried out elsewhere (nuclear med/endoscopy/clin investigation unit). 4 labs were unaware of testing in their hospital. 8 labs did not fill in this part of the questionnaire. 8. Assays for the gut hormones VIP, gastrin and glucagon should be available. Diarrhoea due to hormone secreting tumours is extremely rare and testing for the presence of excess vasoactive intestinal peptide (VIP), gastrin or glucagon in plasma is recommended only in the presence of high volume watery diarrhoea when other causes of diarrhoea have been excluded (C). 100 All 16 labs sent samples for VIP, gastrin and glucagon to a single reference lab. 4 labs <10/year, 6 labs 10-19/year, 3 labs 20-49/year, 2 labs /year. All labs offered 5-HIAA. Workloads : 25–600*/year (* includes work for other labs). 17/21 labs replied (81%) : 6 teaching hospitals, 11 district general hospitals. Conclusion Hospitals met 5 of the 8 defined standards in the audit. The guidelines (1) and this audit should be helpful to labs still under pressure to carry out 3- day faecal fat analyses. Only one lab in the region was involved in performing breath tests but this may be an area where more help could be offered to gastroenterologists. An invitation to the labs audited to comment on the standards proposed indicated agreement with the standards ( 3 replies). Acknowledgements/Reference Thank you to all the laboratories that took part in the audit and the audit leads Ms Roberta Goodall and Dr Jeremy Quiney. (1) Thomas PD, Forbes A, Green J, et al. Guidelines for the investigation of chronic diarrhoea. 2 nd edn. Gut 2003; 52 (Suppl V): v1-15