Abstract
Serum immunoglobulin G4 level is a poor predictor of immunoglobulin G4-related disease
Ngwa TN, Law R, Murray D, Chari ST, et al.
Pancreas. Epub ahead of print 13 March 2014. DOI: 10.1097/MPA.0000000000000118.
Immunoglobulin G4-related disease (IgG4-RD) is a chronic fibroinflammatory condition frequently associated with IgG4-positive plasma cell infiltration and increased circulating IgG4. This study assessed the diagnostic utility of serum IgG4 measurement in 6014 patients with a variety of presentations who had IgG4 measured using a latex-enhanced nephelometric immunoassay. Only patients with IgG4 above the upper limit of normal (ULN) (390 patients) were included in analysis.
Of the 390 cases of raised IgG4, only 10% had definite or probable IgG4-RD. The majority of these (25/39) had autoimmune pancreatitis. Although a higher proportion of patients with definite or probable IgG4-RD had significantly raised (2 × ULN) IgG4 (P < 0.05), a receiver operating characteristic curve area under curve of 0.64 and a poor positive predictive value (10%) of a raised IgG4 were both noted.
The study highlights the spectrum of IgG4-related disease, but found elevated IgG4 was a poor predictor of IgG4-RD in an institution-wide cohort. Limitations include retrospective design, reliance on judgement of different clinicians for diagnoses, lack of reasons for measurement of IgG4, and possible misclassification of IgG4-RD with non-classical presentations. Also, the study does not address the use of IgG4 in selected patients with a high probability of IgG4-RD, when the test is likely to be of more value.