Tropical sprue laboratory findings
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]; Associate Editor(s)-in-Chief: Aravind Kuchkuntla, M.B.B.S[3]
Overview
Tropical sprue is a diagnosis of exclusion and there are no specific laboratory findings. Blood smear will show megaloblastic changes in chronic phase of tropical sprue. All the etiologies of malabsorption must be ruled out to consider the diagnosis of tropical sprue.
Laboratory Findings
Tropical sprue is diagnosed based on the following criteria:[1]
- Clinical presentation with chronic non bloody diarrhea with malabsorption
- Presence of malabsorption for two different substances
- Abnormal small intestinal histological findings
- Exclusion of other causes of malabsorption
- Response to treatment with tetracycline and folic acid
All the patients with celiac disease unresponsive to gluten free diet, a diagnosis of tropical sprue must be considered. The lab findings are not specific for tropical sprue as it is a diagnosis of exclusion. [2]
- Patients with ileal involvement will have low vitamin B12 and folate levels.[3]
- Normal transglutaminase, immunoglobulin levels are present.
- Peripheral blood smear will demonstrate megaloblastic picture.
Approach to a Patient With Malabsorption in Tropical Region
| Clinical suspicion of malabsorption syndrome | |||||||||||||||||||||||||||||||||||||||||||||||
| Initial screening perform: •Stool microscopy to rule out infectious causes •D-xylose test to test for the presence of intestinal enterocyte dysfunction •Fecal fat test for detection of steatorrhea | |||||||||||||||||||||||||||||||||||||||||||||||
| If D-Xylose and feacal fat tests are positive, confirmatory tests for malabsoption should be done | |||||||||||||||||||||||||||||||||||||||||||||||
| •Positive antiendomysial antibodies and villous atrophy suggests celiac disease •Positive breath hydrogen test suggests lactase deficiency •Positive microscopy and culture of jejunal aspirate suggests small bowel bacterial overgrowth •Low serum immunoglobulin suggests B-cell deficiency •HIV serology for HIV infection •CT enterography to rule out intestinal inflammatory conditions •Abdomen CT to rule out chronic pancreatitis | |||||||||||||||||||||||||||||||||||||||||||||||
| Once other possibilities are ruled out, suspect diagnosis of tropical sprue | |||||||||||||||||||||||||||||||||||||||||||||||
| Start tetracycline therapy Improvement of symptoms with tetracycline confirms the diagnosis | |||||||||||||||||||||||||||||||||||||||||||||||
Laboratory Investigations in Patient with Malabsorption
- Stool microscopy will demonstrate the presence of protozoa like giardia, ova, cyst and other infective agents.
- Fecal fat study to diagnose steatorrhea.
- Low elastase and chymotrypsin is an indicator of pancreatic insufficiency.[4]
- IgA tissue transglutaminase or IgA antiendomysium assay for gluten sensitive enteropathy.
- Blood tests may reveal anaemia, high ESR or low albumin.
- D-Xylose test is useful in determining enterocyte function.
- CT abdomen is helpful in the diagnosis of inflammatory bowel disease and pancreatitis.
References
- ↑ Walker MM (2003). “What is tropical sprue?”. J Gastroenterol Hepatol. 18 (8): 887–90. PMID 12859716.
- ↑ Bonnefoy S, Chauvin A, Galéano-Cassaz C, Camilleri-Broet S, Jacquet SF, Carmoi T; et al. (2012). “[Tropical sprue in an expatriate]”. Rev Med Interne. 33 (5): 284–7. doi:10.1016/j.revmed.2012.01.015. PMID 22405324.
- ↑ Misra RC, Kasthuri D, Chuttani HK (1967). “Correlation of clinical, biochemical, radiological, and histological findings in tropical sprue”. J Trop Med Hyg. 70 (1): 6–10. PMID 6016817.
- ↑ Thomas P, Forbes A, Green J, Howdle P, Long R, Playford R, Sheridan M, Stevens R, Valori R, Walters J, Addison G, Hill P, Brydon G (2003). “Guidelines for the investigation of chronic diarrhoea, 2nd edition”. Gut. 52 Suppl 5: v1–15. PMID 12801941.[1].
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