Acta Diabetol 32: 137-142, 1995 ACTA DIABETOLOGICA © Springer-Verlag 1995 Originals HI,A-DQ screening for risk assessment of insulin dependent diabetes in northern Italy V. Lampasona l, M. Ferrari 1, E. Bonifacio 2, M. R. Pastore 2, P. Carrera 1, A. Sergi 2, S. Genovese 2, M. Trucco 3, J. Dorman 4, E. Bosi 2 1 Department of Laboratory Medicine, Molecular Biology Unit, Istituto Scientifico San Raffaele, via Oigettina 60, 1-20132 Milan, Italy 2 Department of Internal Medicine, Istituto Scientifico San Raffaele, Milan, Italy 3 Division of Immunogenetics, Department of Pediatrics, University of Pittsburgh, Rangos Research Center, Children's Hospital of Pitts- burgh, Pittsburgh, PA 15261, USA 4 Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA Received: 25 January 1995 / Accepted in revised form: 28 April 1995 Abstract. Genetic markers may be used to improve the prediction of insulin-dependent diabetes mellitus (type 1) in individuals with islet autoantibodies. In order to develop a risk assessment strategy for the Lombardy region of northern Italy based on genetic and immunological mark- ers, we analyzed HLA DQA1 and DQB1 alleles in 60 type 1 probands and their first-degree relatives and 65 un- related control subjects from the same area using polyme- rase chain reaction (PCR) and oligonucleotide probes. The major risk haplotypes were DQA 1 • 0501-DQB 1 * 0201 (39.1% of diabetic vs 8.9% of non-diabetic haplotypes) and DQA 1 * 0301-DQB 1 * 0302 (20% of diabetic vs 7.1% of non-diabetic haplotypes). Stratified analysis showed DQA 1 * 0102-DQB 1 * 0502 also to be associated with type 1 susceptibility when found together with DQA 1 * 0501- DQB1.0201 or DQA1 *0301-DQB1 *0302. One type 1 patient had the type 1-protective DQAl*0102- DQB 1 * 0602 haplotype. Overall, 88% of patients and 20% of unrelated control subjects had either DQAI*0501- DQB 1 * 0201 or DQA 1 * 0301-DQB 1 * 0302 in the absence of DQAI*0102-DQBI*0602. These data suggest that typing for markers identifying these three haplotypes in the Lombardy population will achieve a sensitivity of al- most 90% and exclude 80% of children from subsequent islet autoantibody testing. Key words: Insulin-dependent diabetes mellitus - HLA - Genetic markers - Risk assessment Introduction The development and successful implementation of inter- vention therapies for the prevention of insulin-dependent diabetes mellitus (type 1) relies upon the accurate selec- tion of individuals at high risk for developing disease [1-3]. Current strategies utilize islet autoantibody mark- Correspondence to: V. Lampasona ers for risk assessment. These are based on prospective studies in first-degree relatives of type 1 patients [4-6], but only around 10% of future cases can be identified [7]. Although maximum sensitivity will be achieved by screen- ing the childhood population, the diabetes risk in antibody- positive individuals without a family history may be too low to justify intervention trials [8]. Using combinations of islet antibody markers is likely to improve both speci- ficity and sensitivity [9-11]. Nevertheless, the efficiency of antibody screening will be reduced if the age of onset of antibodies in the circulation varies between individu- als. Sequential antibody analysis from birth [12] are few in number, and it is unclear whether or not single screen- ing at an early age will be sufficient to identify most fu- ture type 1 cases or sequential screening strategies will be necessary. Preselection based on genetic markers prior to antibody testing may facilitate both these studies and sub- sequent antibody screening strategies and, moreover, im- prove type 1 risk assessment. This will be an efficient approach to screening provided that the genetic markers chosen have sufficient sensitivity and specificity. The strongest genetic contribution to type 1 diabetes is associated with the HLA DQA1 and DQB 1 loci [13-16], which code for c~- and ~-chains of the HLA-DQ hetero- dimer. In particular, the combinations of DQA1 and DQB 1 alleles coding for arginine in position 52 on the DQ-cz molecule [15] and amino acids other than aspartic acid in position 57 of the DQ-~ molecule [13, 14], have been shown to confer susceptibility. This combination can oc- cur directly in cis on certain HLA-DQA1-DQB1 haplo- types or by the combination in trans of DQA1 and DQB 1 molecules encoded on separate haplotypes. In caucasoid populations, the majority of type 1 patients have DQA1 and DQB 1 alleles, with the capacity of forming at least two susceptible heterodimers [ 16-20]. The aim of this study was to develop a genetic screen- ing strategy for the Lombardy region of northern Italy based upon HLA class II typing, which will identify the majority of type 1 patients while excluding a substantial proportion of the population from subsequent antibody testing. To determine which DQA1 and DQB 1 haplotypes