Comparison of classic sweat test and crystallization test in diagnosis of cystic fibrosis.

OBJECTIVE: Sweat chloride measurement is considered a standard diagnostic tool for cystic fibrosis (CF). This study was performed to compare sweat chloride values obtained by quantitative pilocarpine iontophoresis (classic test) with sweat crystallization detected by direct observation of a drop of perspiration under light microscopy in patients with and without CF. METHODS: The tests using both techniques were performed simultaneously in patients with and without CF. Cutoff values of ≥60 mmol/L of chloride concentration for the classic sweat test was considered for diagnosis of CF. In crystallization method, observation of typical dendritic forms of salt crystals under light microscopy was interpreted positive. FINDINGS: Sixty patients suspected to CF (31 males and 29 females) with age range of 9 months to 2 years underwent the sweat test using both techniques. Median sweat chloride values was 26.13+10.85 in group with negative and 72.76+12.78 mmol/L in group with positive sweat test, respectively. All the patients who had positive sweat test in classic method showed typical dendritic forms of salt crystal in sweat crystallization test, which provided the test with 100% sensitivity (95%CI: 93.1-100). Only one of the 31 subjects with negative results for classic sweat test had positive result for crystallization sweat test, which provided the test with 96.7% specificity (95%CI: 92.9-100). Time spent to perform the crystallization test was significantly shorter than the classic method whereas its cost was also lower than the second method. CONCLUSION: There was a good correspondence between two studied methods of sweat test. These results suggested the sweat crystallization test as an alternative test for detecting CF disease with high sensitivity and specificity.

Prevalence of occult celiac disease in healthy Iranian school age children.

BACKGROUND:   Several studies have shown the prevalence of celiac disease (CD) to be around 1% in Iran, which is similar to the worldwide prevalence. There is scant information on occult CD in apparently healthy school age children. This study, as the first such study in Iran, aims to determine the prevalence of occult CD in healthy Iranian school age children. METHODS: In this cross-sectional study, we screened healthy school age children for CD by serum IgA and IgA anti-tissue transglutaminase antibody (tTG) levels. Measurement of these antibodies was by enzyme linked immunosorbent assay. A recheck of positive tTG tests was performed and patients who tested positive underwent endoscopic duodenal biopsies. The biopsy samples were scored according to the Marsh classification by an experienced pathologist. RESULTS: A total of 634 children (314 males, 320 females; mean age: 12.8 years) were included in the study. All children and/or their parents completed a questionnaire and children underwent an initial physical examination to determine study eligibility. Positive serum tTG was noted in 3 (0.5%; 2 females) out of 634 patients. Duodenal biopsies were consistent with CD in these 3 subjects. The mean age of patients with CD was 14.3 years (range: 12-17 years). The female to male ratio was 2:1. These cases had no signs and symptoms, but a gluten-free diet was recommended according to pathologic changes in their small bowels and results of the tTG test. CONCLUSION: The prevalence of occult CD in these children is 0.5%, which is half of the prevalence of CD in Iranian adults. The anti-tTG concentration at initial serological CD screening is highly informative in determining occult cases of CD. The question is whether all non-symptomatic cases should be treated with a gluten-free diet or not.

Prevalence of celiac disease in Iranian children with recurrent abdominal pain referred to a pediatric referral center.

OBJECTIVE: Clinical features of Iranian children with celiac disease (CD) are still unknown and there is scant information about atypical presentation of celiac disease from Iran. The aim of this study was to determine prevalence of CD in Iranian children presenting with functional abdominal pain (FAP). METHODS: In this cross-sectional study, 301 children affected by FAP were screened for CD by anti-tissue transglutaminase antibody (tTG IgA). IgA antibody was also measured to exclude IgA deficiency. The antibodies were measured by enzyme linked immunosorbent assay. Diagnosis of CD was confirmed by duodenal biopsy that was scored according to the Marsh classification in cases with abnormal titer of tTG antibody. FINDINGS: A total of 301 children (138 males, 163 females) with FAP were studied. Endoscopic duodenal biopsy was taken for patients with positive and borderline tTG test. Two out of 301 cases were IgA deficient and celiac disease was suspected for one of them based on histological findings. Four out of 299 patients with normal IgA had abnormal tTG titer; intermediate ranges (16-23 U/ml) were detected in 1 and positive ranges (≥24 U/ml) in 3 cases. CD was suggested in all patients with abnormal titer of tTG (1.33%) based on histological findings. CONCLUSION: The prevalence of celiac disease in children with FAP is estimated 1.3% (nearly 2 times higher than in normal population) in Iran.