Ryu, Euijung

Abstract Background: Previous comparisons of monoclonal protein quantification identified a bias between serum protein electrophoresis (SPEP) and immunonephelometry (NEPH). Methods: We reviewed data from 2845 patients in whom a single sample provided a γ fraction M-spike by SPEP, a heavy chain isotype by immunofixation electrophoresis (IFE), and an Ig quantification by NEPH. We examined the relationship between SPEP and NEPH. Selected sera with high monoclonal protein concentrations were diluted and reassessed. Results: For all isotypes, the relationship between SPEP and NEPH was best fitted with cubic curves. We determined the concentrations of each isotype that fitted a linear relationship. IgA had the best correspondence (slope 0.92, 95% CI 0.87–1.02), whereas IgM demonstrated a systematic bias of higher values by NEPH (slope 1.80, 95% CI 1.68–1.92). IgG demonstrated a nonlinear relationship between SPEP and NEPH, with a linear region <19.2 g/L having a slope of 0.83 (95% CI 0.79–0.89) and a second linear region having a slope of 1.47 (95% CI 1.39–1.53) at higher concentrations. Dilutions of high-concentration IgG monoclonal proteins were linear by NEPH and nonlinear by SPEP. Conclusions: There are systematic differences in the quantification of monoclonal IgM and IgG by SPEP and NEPH. The bias in IgM is from NEPH overestimation. The nonlinearity of SPEP at high monoclonal IgG concentrations may obscure changes in plasma cell populations. Clinicians should be made aware of the biases and nonlinearity in these tests to make proper conclusions regarding treatment response.

Abstract Context: The association between acute pancreatitis and primary hyperparathyroidism (PHPT) is controversial. Objective: The aim of the study was to address the incidence and disease characteristics of acute pancreatitis in PHPT from a large inception cohort of community residents. Design and Setting: Patients with acute pancreatitis were identified in an Olmsted County, Minnesota, cohort of PHPT subjects diagnosed from 1965–2001 and compared to matched control subjects. Main Outcome Measures: The estimated rate of developing acute pancreatitis was calculated by person-years method. Cox models assessed the effect of PHPT disease status on the development of acute pancreatitis. Results: Of 684 patients with PHPT, 10 patients (1.5%) developed acute pancreatitis, compared to 32 of 1364 control patients (2.3%). The estimated rate of development of acute pancreatitis in PHPT was 114 per 100,000 person-years, compared to 140 per 100,000 person-years in control subjects (P = 0.56). The estimated hazard ratio of acute pancreatitis for PHPT relative to the control subjects was 0.84 (P = 0.89). The majority of subjects with PHPT and acute pancreatitis were women (n = 7), and the mean age was 70.6 yr at the time of acute pancreatitis. PHPT was present an average of 137 months before the development of acute pancreatitis, and contributing causes for acute pancreatitis were in identified in four patients. Maximal serum calcium levels in PHPT were not significantly associated with the development of acute pancreatitis. Conclusions: Acute pancreatitis was not increased in community patients with PHPT, and therefore, there does not appear to be a causal relationship between PHPT and acute pancreatitis.