160 likes | 235 Vues
C hecking the quality of diagnostic tools. Zrinjka Mišak Referral Centre for Paediatric Gastroenteorology and Nutrition Children’s Hospital Zagreb Zagreb, Croatia. ESPGHAN guidelines for the diagnosis of coeliac disease in children and adolescents. An evidence-based approach
E N D
Checking the quality of diagnostic tools Zrinjka Mišak Referral Centre for Paediatric Gastroenteorology and Nutrition Children’s Hospital Zagreb Zagreb, Croatia
ESPGHAN guidelines for the diagnosis of coeliac disease in children and adolescents. An evidence-based approach Husby S, Koletzko S, Korponay-Szabó IR, Mearin ML, Phillips A, Shamir R, Troncone R, Giersiepen K, Branski D, Catassi C, Lelgeman M, Mäki M, Ribes-Koninckx C, Ventura A, Zimmer KP. (The ESPGHAN Working Group on Coeliac Disease Diagnosis) J Pediatr Gastroenterol Nutr, 2012
The importance of serology ESPGHAN guidelines Recommendation 8.3.1: • Histological assessment may be omitted in symptomatic cases, who have high IgA anti-TG2 levels (10 x above uppernormal limit), verified by EMA positivity, and are HLA DQ2 and/or DQ8heterodimer positive.
Anti-TG2 • Numerical values obtained with different kits - differ • The valuesdepend on: • the source (human or animal) • quality and exposure of the antigen • calibrators • buffers • measuring methods • cut-off values • calculation mode of the results
Anti-TG2 • Despite of differences, many commercial anti-TG2 tests have equally high sensitivity and specificity • Inter-laboratory variability also exists • There may be considerable batch to batch variability within commercial anti-TG2 assays which needs to be monitored by the use of independent quality control material
Anti-TG2 ESPGHAN guidelines: Evidence statement • The numeric values obtained with different test kits in anti-TG2 or anti-DGPantibody measurements cannot be directly compared as they may differ intheir measurement principles, calibrators and calculation mode of results.
ESPGHAN guidelines Recommendation 7.4.4: • Anti-TG2 and anti-DGP laboratory test results should be reported asnumeric values together with specification of the immunoglobulin classmeasured, the manufacturer, the cut-off value defined for the specific test kit,and, (if available) the level of ’high’ antibody values. • It is not sufficient to stateonly positivity or negativity. Information on the source of the antigen (natural,recombinant, human, non-human) should be provided for in-house methods.
EMA • in experienced hands has the highest specificity and positive likelihood ratio for CD among currently available serology tools. • It is more likely that CD is present if the EMA is positive than if another CD antibody result is positive. • EMA tests require microscopicalevaluation and may be subject to interobservervariability • It islabourintensive, and the substrates (monkey oesophagus, umbilicus) are limited
ESPGHAN guidelines Recommendation 7.4.5: • (↑↑) Reports on EMA results should contain • the specification of the investigatedimmunoglobulin class, • the interpretation of the result (positive or negative), • the cut-off dilution and • the specification of the substrate tissue. • It is also useful tohave the information on the highest dilution still positive.
The role of the laboratory ESPGHAN guidelines: Statement: • The expertise of the laboratory and the selection of the test kit influence the accuracy of CD antibody tests.
ESPGHAN guidelines Recommendation 7.4.3: • (↑↑) Laboratories providing CD antibody test results for diagnostic use shouldcontinuously participate in quality control programme at national or Europeanlevel.
Our experience – Children’s Hospital Zagreb, Croatia • Intra-laboratory control • Control samples in every set of tests • Inter-laboratory control • Together with other University Hospital in Zagreb and some German medical centres
Biopsy ESPGHAN guidelines Recommendation 8.3.9: • (↑) It is recommended that the pathology report includes: • description of the orientation • evaluation of villi (normal or degree of atrophy) • evaluation of crypts • villous/crypt ratio • number of IELs • Grading according to Marsh-Oberhuber is recommended.
Our experience – Children’s Hospital Zagreb, Croatia • Before - one pathologist at the School of Medicine • Courses, seminars... • Now – more pathologists at university centers and general Hospitals
Suggestions Serology • Sharing the information on how to validate the test and to do intra-laboratory control • Set up local inter-laboratory controls • Network to do inter-laboratory control • Comparative evaluation • when comparing between data sets with different units or widely different means - coefficient of variation should be used (Cv = Standard Deviation / Mean) Biopsy • Sharing the knowledge on how to interpret biopsies