Interference by heterophilic antibodies in immunoassays: wrong increase of myoglobin values.

Aim of this work is to illustrate how analytical interference in immunoassay may produce serious errors in clinical laboratory results. The sophisticated quality assurance schemes used in many laboratories do not identify erroneous results arising from aberrant samples. Recently attention has been focused on the incidence and implication of false-positive results arising from the presence of certain substances in a patient's serum that interfere with one or more steps in immunoassays. In this paper, we present the case of a 92 year-old woman whose plasma myoglobin concentrations falsely increased when measured using the Beckman Access assay. We demonstrated that heterophilic antibodies accounted for the falsely increased myoglobin values, and we suggest how to resolve such situations.

Anti-68 kDa antibodies in autoimmune sensorineural hearing loss: are these autoantibodies really a diagnostic tool?

OBJECTIVES: Autoimmune sensorineural hearing loss (ASNHL) is a relatively rare disorder which can lead to total deafness. At present, no specific laboratory test with adequate sensitivity and specificity is available to confirm the clinical suspicion of ASNHL. The aim of this study was to identify if evaluation of anti-hsp70 antibodies is an accurate diagnostic tool in patients affected by ASNHL. STUDY DESIGN: Prospective study. METHODS: During 4-year (2001-2005), all patients with SNHL who were referred to the Eye, Ear, Nose and Throat Department of Parma University, Italy, underwent specific tests to determine the autoimmune origin of the disease. Patients with a consistent suspicion of ASNHL underwent the routine serologic tests and a test for determination of anti-hsp70 antibodies. The same patients were divided into three groups: (1) idiopathic ASNHL; (2) ASNHL associated with ocular inflammation, i.e. Cogan's Syndrome; (3) ASNHL associated with a systemic autoimmune disease (SAD). The control group included: (1) healthy subjects; and (2) patients affected by SAD, without any ocular or audiovestibular disease. RESULTS: 88 subjects (67 patients, defined as "study group", and 21 controls) were evaluated. Anti-hsp70 antibodies were isolated in 52% of the study group patients, and in 4% of the control group (chi2 = 13.009, p < 0.01). In the idiopathic ASNHL patients, 59.5% were found positive for anti-hsp70 antibodies. About 50% of patients affected by CS and 37.5% of patients affected by SAD with SNHL were found positive. In the control group, anti-hsp70 antibodies were found in 8.3% of healthy subjects and in none of the patients with SAD and no hearing loss. CONCLUSIONS: The present study confirms the value of the anti-hsp70 test in the serological diagnosis of autoimmune hearing loss. It is still the only available diagnostic marker that identifies an autoimmune origin of hearing loss.

An italian multicenter study for application of a diagnostic algorithm in autoantibody testing.

The presence in the serum of specific autoantibodies, such as antinuclear antibodies (ANA), anti-double-stranded DNA (anti-dsDNA), and antiextractable nuclear antigens (anti-ENA), is one of the diagnostic criteria for autoimmune rheumatic disease, and the requests for these tests in the last few years have grown remarkably. A guideline for reducing clinically inappropriate requests in autoantibody testing (ANA, anti-dsDNA, anti-ENA) has been applied in the Parma Hospital since 2007. The results for the period January-December 2007 were compared to those of the previous period January-December 2006, and a significant reduction in the number of anti-dsDNA (23.9%) and anti-ENA (20.7%) was found. The aim of this study was to assess the applicability of a similar guideline in a wide area (Parma, Modena, Piacenza, Reggio-Emilia) with reference to the diagnosis of autoimmune rheumatic disease. This project, supported by a regional grant for innovative research projects, was started in January 2008 and consists of three different steps: (1) a study group of clinicians and laboratory physicians to evaluate the diagnostic criteria, the analytical procedures, and the number of tests performed in different hospitals; (2) developing common guidelines for autoantibody testing that takes into account the different clinical needs with the aim of improving efficiency and clinical effectiveness of diagnosis and monitoring; and (3) assessing compliance with the guidelines in the different hospitals that are evaluating the second-level test (anti-dsDNA, anti-ENA) decrease. We think that the validation of guidelines for the laboratory diagnosis of autoimmune rheumatic disease can represent a tool for improving patients' outcomes and economic efficiency.