Título: "The diagnostic utility of serum IgG4
concentrations in IgG4-related disease"
Autores: Mollie N Carruthers, Arezou Khosroshahi,
Tamara Augustin, Vikram Deshpande, John H Stone.
Carruthers MN, Khosroshahi A, Augustin T, et al.
Ann Rheum Dis 2015; 74 :14 – 18.
We evaluated the sensitivity, speci fi city and positive and negative predictive values of elevated serum IgG4 concentrations for the diagnosis of IgG4-RD.
Between 2001 and 2011, 190 unique patients had elevated serum IgG4 measurements. We reviewed electronic medical records to determine the indication for IgG4 measurement and underlying clinical diagnosis. Additionally, we reviewed the records of 190 other randomly selected patients from a pool of 3360 with normal results, to evaluate test characteristics of the IgG4 measurement.
Among 380 patients analysed, 72 had either probable or de fi nite IgG4-RD. Sixty- fi ve of the 72 IgG4-RD patients had elevated serum IgG4 concentrations (mean: 405 mg/dL; range 140 – 2000 mg/dL), for a sensitivity of 90%. Among the 308 subjects without IgG4-RD, 125 had elevated IgG4 (mean: 234 mg/dL; range 135 – 1180 mg/dL) and 183 had normal IgG4 concentrations, for a speci fi city of 60%. The negative predictive value of a serum IgG4 assay was 96%, but the positive predictive value only 34%. Analysis of the serum IgG4/total IgG ratio did not improve these test characteristics. Doubling the cutoff for IgG4 improved speci fi city (91%) but decreased sensitivity to 35%.
Multiple non-IgG4-RD conditions are associated with elevated serum IgG4, leading to poor speci fi city and low positive predictive value for this test. A substantial subset of patients with biopsy-proven IgG4-RD do not have elevated serum IgG4. Neither doubling the cutoff for serum IgG4 nor examining the serum IgG4/IgG ratio improves the overall test characteristics for the diagnosis of IgG4-RD.