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What is the probability of false positive and false negative results from the serological tests?**

Vijay Kumar, M.D., Research Associate Professor at the University of Buffalo and President and Director of IMMCO Diagnostics: The three serological tests that are used for diagnosing celiac disease are:

Each of these three tests provide a certain degree of reliability for diagnosing CD. Of these, endomysial antibody is the most specific test. The following table is taken from our studies (Lerner, Kumar, Iancu, Immunological diagnosis of childhood coeliac disease: comparison between antigliadin, antireticulin and antiendomysial antibodies).

  % of Sensitivity % of Specificity Predictive Value % Pos Predictive Value % Neg
EMA 97% 98% 97% 98%
ARA 65% 100% 100% 72%
IgG AGA 88% 92% 88% 92%
IgA AGA 52% 94% 87% 74%

 

The following definitions related to sensitivity, specificity, positive and negative predictive values may help:

Sensitivity is the probability of a positive test result in a patient with disease. Specificity is the probability of negative test result in a patient without disease. Positive predictive value is the probability of disease in a patient with positive test result. Negative predictive value is the probability of no disease in a patient with negative test result.

Karoly Horvath, M.D., Ph.D., Associate Professor of Pediatrics; Director, Peds GI & Nutrition Laboratory; University of Maryland at Baltimore: The summary below shows the results of the main serological tests based on several publications including 388 patients with CD, and 771 healthy subjects.

 

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SENSITIVITY- the proportion of subjects with the disease who have a positive test. It indicates how good a test is at identifying the diseased:

  Percentage of - IgA AGA Percentage of - IgG AGA Percentage of - IgA EMA
Average 78% 79% 97%
Range 46-100% 57-94% 89-100%



SPECIFICITY- the proportion of subjects without the disease who have a negative test. It indicates how good a test is at identifying the non-diseased:

  Percentage of - IgA AGA Percentage of - IgG AGA Percentage of - IgA EMA
Average 92% 84% 98.5%
Range 84-100% 52-98% 97-100%



POSITIVE PREDICTIVE VALUE- the probability that a person with positive results actually has the disease:

  Percentage of - IgA AGA Percentage of - IgG AGA Percentage of - IgA EMA
Average 72% 57% 92%
Range 45-100% 42-76% 91-94%



NEGATIVE PREDICTIVE VALUE- the probability that a person with negative results does not have the disease:

  Percentage of - IgA AGA Percentage of - IgG AGA Percentage of - IgA EMA
Average 94% 94% 100%
Range 89-100% 83-99% 100%



References:
McMillan SA, Haughton DJ, Biggart JD, Edgar JD, Porter KG, McNeill TA. Predictive value for coeliac disease of antibodies to gliadin, endomysium, and jejunum in patients attending for jejunal biopsy. Brit Med J 1991;303:1163-1165
Ferreira M, Lloyd Davies S, Butler M, Scott D, Clark M, Kumar P. Endomysial antibody: is it the best screening test for coeliac disease? Gut 1992;33:1633-1637.
Khoshoo V, Bhan MK, Puri S, Jain R, Jayashree S, Bhatnagar S, Kumar R, Stintzing G. Serum antigliadin antibody profile in childhood protracted diarrhea due to coeliac disease and other causes in a developing country. Scand J Gastroenterol 1989;24:1212-1216.
Chan KN, Phillips AD, Mirakian R, Walker-Smith JA. Endomysial antibody screening in children. J Pediatr Gastroenterol Nutr 1994;18:316-320.
Bode S, Weile B, Krasilnikoff PA, Gdmand-Hyer E. The diagnostic value of the gliadin antibody testing celiac disease in children: a prospective study. J Pediatr Gastroenterol Nutr 1993;17:260-264.
Calabuig M, Torregosa R, Polo P, Tom s C, Alvarez V, Garcia-Vila A, Brines J, Vilar P, Farr C, Varea V. Serological markers and celiac disease: a new diagnostic approach ? J Pediatr Gastroenterol Nutr 1990;10:435-442.

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1 Response:

 
sandra despain
Rating: ratingfullratingfullratingfullratingfullratingempty Unrated
said this on
16 Nov 2009 4:58:58 PM PST
Not a bad article but missing one important bit of information. Patient can be iga deficient and that would result in possible false negative results on IGA EGA, IGA ARA and IGA EME. Reflecting that a small intestinal biopsy would be the best approach.




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