Clinical phenotypes of patients with anti-DFS70/LEDGF antibodies in a routine ANA referral cohort

DFS70/LEDGFp75: An Enigmatic Autoantigen at the Interface between Autoimmunity, AIDS, and Cancer

Clinical and diagnostic laboratories often encounter patient sera containing antinuclear antibodies (ANAs) that produce a nuclear dense fine speckled immunofluorescence pattern on HEp-2 cells. These autoantibodies usually target the dense fine speckled protein of 70 kDa (DFS70), commonly known as lens epithelium-derived growth factor p75 (LEDGFp75). Anti-DFS70/LEDGFp75 autoantibodies have recently attracted much interest because of their relatively common occurrence in sera from patients with positive ANA tests with no clinical evidence of systemic autoimmune rheumatic disease (SARD). Their presence has been documented primarily in patients with diverse non-SARD inflammatory conditions and “apparently healthy” individuals. While there is circumstantial evidence that depending on the context these autoantibodies could play protective, pathogenic, or sensor roles, their significance remains elusive. DFS70/LEDGFp75 has emerged during the past decade as a stress transcription co-activator relevant to HIV integration, cancer, and inflammation. It is not clear, however, what makes this protein the target of such a common autoantibody response. We suggest that a better understanding of DFS70/LEDGFp75 biology is key to elucidating the significance of its associated autoantibodies. Here, we discuss briefly our current understanding of this enigmatic autoantigen and potential scenarios leading to its targeting by the immune system.

Diagnostic utility of unidentified precipitin lines (UPLs) in immune precipitation assays

Unidentified precipitin lines (UPLs) are lines in immune precipitin assays which do not characterise with known extractable nuclear antigen (ENA) antibodies. Currently, the clinical significance of UPLs is uncertain.The aim of this study was to determine the clinical and laboratory correlates of UPLs detected over a 3 year period in a regional immunopathology laboratory.A total of 144 patients with UPLs on ENA testing were retrospectively analysed.ENA by counterimmunoelectrophoresis (CIE) was performed on 11,869 patient samples with further characterisation being performed for 1437 positive results. Ten percent of the positive ENAs demonstrated UPLs. The majority of patients with UPLs were female (71%) with an average age of 60 years. Precipitin lines for both continuously growing myeloid cell line K562 and rabbit thymus extract (RTE) were more frequent (47%), compared to K562 only (41%) or RTE only (12%). The most common antinuclear antibody (ANA) patterns associated with UPLs were speckled (29%), homogenous (16%), mixed patterns (14%), with 30% negative ANA and 5% showing cytoplasmic patterns (Golgi, GWB, mitochondrial). Both ANA positive and ANA negative patients with UPLs were generally associated with connective tissue and autoimmune disease with the majority demonstrating a positive association of UPLs with Ro52 and/or Ro60/SSA detected by Euroimmun line immunoassay. UPLs frequently seen with a negative ANA were also identified in renal disease, pulmonary fibrosis/bronchiectasis and malignancy/lymphoma.UPLs have uncertain diagnostic utility at this stage and further work needs to be done to clarify this question. UPLs were found in systemic and organ specific autoimmune disease, renal, pulmonary and neoplastic disorders. UPLs can occur in both ANA positive and ANA negative sera. The nature of the precipitating antigen in UPLs is still obscure.

Anti-nuclear antibody screening using HEp-2 cells

The American College of Rheumatology position statement on ANA testing stipulates the use of IIF as the gold standard method for ANA screening(1). Although IIF is an excellent screening test in expert hands, the technical difficulties of processing and reading IIF slides--such as the labor intensive slide processing, manual reading, the need for experienced, trained technologists and the use of dark room--make the IIF method difficult to fit in the workflow of modern, automated laboratories. The first and crucial step towards high quality ANA screening is careful slide processing. This procedure is labor intensive, and requires full understanding of the process, as well as attention to details and experience. Slide reading is performed by fluorescent microscopy in dark rooms, and is done by trained technologists who are familiar with the various patterns, in the context of cell cycle and the morphology of interphase and dividing cells. Provided that IIF is the first line screening tool for SARD, understanding the steps to correctly perform this technique is critical. Recently, digital imaging systems have been developed for the automated reading of IIF slides. These systems, such as the NOVA View Automated Fluorescent Microscope, are designed to streamline the routine IIF workflow. NOVA View acquires and stores high resolution digital images of the wells, thereby separating image acquisition from interpretation; images are viewed an interpreted on high resolution computer monitors. It stores images for future reference and supports the operator's interpretation by providing fluorescent light intensity data on the images. It also preliminarily categorizes results as positive or negative, and provides pattern recognition for positive samples. In summary, it eliminates the need for darkroom, and automates and streamlines the IIF reading/interpretation workflow. Most importantly, it increases consistency between readers and readings. Moreover, with the use of barcoded slides, transcription errors are eliminated by providing sample traceability and positive patient identification. This results in increased patient data integrity and safety. The overall goal of this video is to demonstrate the IIF procedure, including slide processing, identification of common IIF patterns, and the introduction of new advancements to simplify and harmonize this technique.

Clinical and serological features of patients referred through a rheumatology triage system because of positive antinuclear antibodies

Background

The referral of patients with positive anti-nuclear antibody (ANA) tests has been criticized as an inappropriate use of medical resources. The utility of a positive ANA test in a central triage (CT) system was studied by determining the autoantibody profiles and clinical diagnoses of patients referred to rheumatologists through a CT system because of a positive ANA test.

Methods

Patients that met three criteria were included: (1) referred to Rheumatology CT over a three year interval; (2) reason for referral was a “positive ANA”; (3) were evaluated by a certified rheumatologist. The CT clinical database was used to obtain demographic and clinical information and a serological database was used to retrieve specific ANA and/or extractable nuclear antigen (ENA) test results. Clinical information was extracted from the consulting rheumatologist's report.

Results

15,357 patients were referred through the CT system; 643 (4.1%) of these because of a positive ANA and of these 263 (40.9%) were evaluated by a certified rheumatologist. In 63/263 (24%) of ANA positive patients, the specialist provided a diagnosis of an ANA associated rheumatic disease (AARD) while 69 (26.2%) had no evidence of any disease; 102 (38.8%) had other rheumatologic diagnoses and 29 (11%) had conditions that did not meet AARD classification criteria. Of ANA positive archived sera, 15.1% were anti-DFS70 positive and 91.2% of these did not have an AARD.

Conclusions

This is the first study to evaluate the serological and clinical features of patients referred through a CT system because of a positive ANA. The spectrum of autoantibody specificities was wide with anti-Ro52/TRIM21 being the most common autoantibody detected. Approximately 15% of referrals had only antibodies to DFS70, the vast majority of which did not have clinical evidence for an AARD. These findings provide insight into the utility of autoantibody testing in a CT system.

A comparison of anti-nuclear antibody quantification using automated enzyme immunoassays and immunofluorescence assays

Anti-nuclear antibodies (ANA) have traditionally been evaluated using indirect fluorescence assays (IFA) with HEp-2 cells. Quantitative immunoassays (EIA) have replaced the use of HEp-2 cells in some laboratories. Here, we evaluated ANA in 400 consecutive and unselected routinely referred patients using IFA and automated EIA techniques. The IFA results generated by two independent laboratories were compared with the EIA results from antibodies against double-stranded DNA (dsDNA), from ANA screening, and from tests of the seven included subantigens. The final IFA and EIA results for 386 unique patients were compared. The majority of the results were the same between the two methods (n = 325, 84%); however, 8% (n = 30) yielded equivocal results (equivocal-negative and equivocal-positive) and 8% (n = 31) yielded divergent results (positive-negative). The results showed fairly good agreement, with Cohen's kappa value of 0.30 (95% confidence interval (CI) = 0.14–0.46), which decreased to 0.23 (95% CI = 0.06–0.40) when the results for dsDNA were omitted. The EIA method was less reliable for assessing nuclear and speckled reactivity patterns, whereas the IFA method presented difficulties detecting dsDNA and Ro activity. The automated EIA method was performed in a similar way to the conventional IFA method using HEp-2 cells; thus, automated EIA may be used as a screening test.