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Data needed

Rashid et al¹ recommend a laboratory test for tissue transglutaminase (tTG) following positive tTG home- test results. Yet they fail to provide any data or rationale to support such unnecessary delays and duplication of costs, which needlessly increase the burden on our health care system. The specificity of the tTG rapid home test is reported to be very close to 100%.^2,3 Although Rashid and colleagues quite rightly decry the unfortunate practice of beginning a gluten-free diet before endoscopic biopsy, the unnecessary delays they recommend might well increase the frequency of patients beginning gluten-free diets prematurely.

As reported, false-negative test results will, predictably, increase in the absence of total immunoglobulin A measurement, owing to the increased incidence of immunoglobulin A deficiency among individuals with celiac disease. This limitation has long been recognized in association with all serology testing for antibodies suggestive of celiac disease. Home tests are, of course, similarly and equally compromised. However, Rashid et al do not provide any data suggesting that the specificity of the home test is compromised. The very study they cite to impugn the home test’s sensitivity reported 100% specificity of this test in the group investigated.²

Admittedly, a reduction in sensitivity is reported for rapid tTG antibody testing when nurses who have not been trained in the administration of this test conduct population screening for celiac disease.² Rashid and colleagues point to the conclusions drawn by Korponay-Szabó et al, who mention that "extra training is needed to improve sensitivity of the test."² This is immediately followed by Rashid et al stating, "There is little data on how well this testing will perform when carried out by the general public."¹ The implication is clear; however, this implicit argument ignores 2 confounding variables.

The first of these obfuscating factors is seen in the very report used to impugn home tests, which states, in part, "The design of the study may have caused further confounding—nurses sent all patients with positive results directly for endoscopy, and they may have been reluctant to do this if the test line was faint."² The nurses’ reluctance might well have resulted from their awareness of the expensive and invasive nature of the endoscopic procedure.

The second variable that Rashid et al seem to overlook is that the home test availability in Canada is accompanied by an Internet link to a 5-minute instructional video (http://celiachometest.com/en/test/video), which provides the very training that the nurses lacked in Korponay-Szabó et al’s investigation.

The lengthy delays to diagnosis, such as an average time frame of 11.7 years to diagnosis and 27% patients with celiac disease consulting 3 or more physicians before confirming diagnosis, are well documented and are reflected in the published work of many of the same authors who contributed to the Rashid et al paper.⁴

Further, as so ably reported by this same group, unnecessary delays can result in debilitating or deadly sequelae.⁴ Such hazards can be mitigated when patients reduce the burden on the health care system by spending their own money on this highly specific testing that, when positive, should lead directly to endoscopic biopsy. The unnecessary cost and delays that arise from repeated serology testing, as recommended by Rashid et al, are not accompanied by any supportive data or rationale and should therefore be viewed with skepticism.

References

1. Rashid M, Butzner JD, Warren R, Molloy M, Case S, Zarkadas M, et al. Home blood testing for celiac disease. Recommendations for management. Can Fam Physician 2009;55:151–3.[Abstract/Free Full Text]
2. Korponay-Szabó IR, Szabados K, Pusztai J, Uhrin K, Ludmány E, Nemes E, et al. Population screening for coeliac disease in primary care by district nurses using a rapid antibody test: diagnostic accuracy and feasibility study. BMJ 2007;335(7632):1244–7. Epub 2007 Dec 6.[Abstract/Free Full Text]
3. Raivio T, Korponay-Szabó IR, Paajanen T, Ashorn M, Iltanen S, Collin P, et al. Comparison of a novel whole blood transglutaminase-based ELISA with a whole blood rapid antibody test and established conventional serologic celiac disease assays. J Pediatr Gastroenterol Nutr 2008;47(5):562–7.[Medline]
4. Cranney A, Zarkadas M, Graham ID, Butzner JD, Rashid M, Warren R, et al. The Canadian Celiac Health Survey. Dig Dis Sci 2007;52(4):1087–95. Epub 2007 Feb 22.[Medline]

This Article Full Text (PDF) Rapid Responses: Submit a response Alert me when this article is cited Alert me when Rapid Responses are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hoggan, R. Search for Related Content PubMed PubMed Citation Articles by Hoggan, R.