ABSTRACT
The demand for testing to detect celiac disease (CD) autoantibodies has increased, together with the cost per case diagnosed, resulting in the adoption of measures to restrict laboratory testing. We designed this study to determine whether opportunistic screening to detect CD-associated autoantibodies had advantages compared to efforts to restrict testing, and to identify the most cost-effective diagnostic strategy. We compared a group of 1678 patients in which autoantibody testing was restricted to cases in which the test referral was considered appropriate (G1) to a group of 2140 patients in which test referrals were not reviewed or restricted (G2). Two algorithms A (quantifying IgA and Tissue transglutaminase IgA [TG-IgA] in all patients), and B (quantifying only TG-IgA in all patients) were used in each group, and the cost-effectiveness of each strategy was calculated. TG-IgA autoantibodies were positive in 62 G1 patients and 69 G2 patients. Among those positive for tissue transglutaminase IgA and endomysial IgA autoantibodies, the proportion of patients with de novo autoantibodies was lower (p=0.028) in G1 (11/62) than in G2 (24/69). Algorithm B required fewer determinations than algorithm A in both G1 (2310 vs 3493; p<0.001) and G2 (2196 vs 4435; p<0.001). With algorithm B the proportion of patients in whom IgA was tested was lower (p<0.001) in G2 (29/2140) than in G1 (617/1678). The lowest cost per case diagnosed (4.63 euros/patient) was found with algorithm B in G2. We conclude that opportunistic screening has advantages compared to efforts in the laboratory to restrict CD diagnostic testing. The most cost-effective strategy was based on the use of an appropriate algorithm.
Subject(s)
Algorithms , Autoantibodies/blood , Celiac Disease/diagnosis , Clinical Laboratory Techniques/methods , Clinical Laboratory Techniques/standards , GTP-Binding Proteins/immunology , Immunoglobulin A/blood , Transglutaminases/immunology , Adolescent , Adult , Celiac Disease/immunology , Child , Child, Preschool , Clinical Laboratory Techniques/economics , Cost-Benefit Analysis , Female , Fluorescent Antibody Technique/economics , Humans , Immunoenzyme Techniques/economics , Luminescent Measurements/economics , Male , Middle Aged , Protein Glutamine gamma Glutamyltransferase 2 , Reagent Kits, Diagnostic , Young AdultABSTRACT
Antinuclear antibodies (ANA) are determined, among other reasons, to identify samples which need a second test to detect the associated specificities. Our aim was to evaluate the clinical and economic impact generated by using an initial dilution for ANA of 1:160. We analyzed all samples for which ANA, anti-ENA and anti-dsDNA were requested over a 1-year period. ANA were detected by indirect immunofluorescence. Anti-ENA were analyzed with a combination of techniques. Anti-dsDNA were detected by radioimmunoassay. Cost analysis was performed by calculating the difference between two cut-offs (ANA 1:40 and 1:160). A total of 13,233 samples were processed for ANA, of which 59.9% were positive with the 1:40 cut-off and 39.2% with the 1:160 cut-off. At ANA titer 1:40, 0.2% of the samples were anti-ENA-positive and 2.2% were anti-dsDNA positive. Only ANA dilutions of 1:160 and higher showed significantly increased positive predictive value for anti-ENA (1.5 versus 0.2, p=0.029) and anti-dsDNA (8.3 versus 2.2, p<0.001) compared to the 1:40 titer. With the 1:160 cut-off, 16.6% fewer ANA tests, 41.8% fewer anti-ENA determinations and 36.4% fewer anti-dsDNA tests would have been needed. The average saving was 0.87 cost-units per sample (1 unit=2.06euro). We conclude that setting the starting dilution for ANA at 1:160 avoids unnecessary studies, increases the positive predictive values of ANA for anti-ENA and anti-dsDNA, and generates clinical and economic benefits.