ABSTRACT
BACKGROUND: The measurement of antinuclear antibodies (ANA) is used in the autoimmune laboratory for the screening of connective tissue diseases (CTD). ANA measurements are mainly performed by indirect immunofluorescence (IIF) on HEp-2 cells or by enzyme immunoassay (EIA). The objective of this study was to clinically evaluate an automated EIA for extractable nuclear antigens (ENA) which lacks anti-dsDNA for the screening of CTD. METHODS: The study involved a total of 170 serum samples, 54 from patients with CTD, 26 from patients with other autoimmune diseases, and 90 from patients with non-autoimmune diseases. For all sera, ANA detection was performed by IIF and by EliA Symphony (Pharmacia Diagnostics, Freiburg, Germany), an ENA screening which detects the following autoantibodies: SSA/Ro, SSB/La, U1RNP (70 kDa, A, C), Scl-70, JO-1, centromere B and Sm. Also, anti-dsDNA (EliA dsDNA, Pharmacia Diagnostics, Freiburg, Germany) was measured on all samples. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), efficiency, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were calculated. RESULTS: Diagnostic efficiency was similar for IIF (82.6%) and EliA Symphony (82.3%), as well as PLR (6.5 for IIF, and 7.3 for Eli Symphony), and NLR (0.35 for IIF, and 0.41 for EliA Symphony). The combined measurement of EliA Symphony and dsDNA increased sensitivity but not PLR. Area under receiver operator characteristic (ROC) curve was similar for IIF (0.847) and EliA Symphony (0.823). CONCLUSIONS: The results of the study demonstrate that EliA Symphony solely or combined with anti-dsDNA detection has an efficiency similar to HEp-2 cells IIF with a cut-off of 1:160 for the diagnosis of CTD.
Subject(s)
Antibodies, Antinuclear/analysis , Connective Tissue Diseases/diagnosis , Connective Tissue Diseases/immunology , Enzyme-Linked Immunosorbent Assay , Fluorescent Antibody Technique, Indirect , Humans , ROC Curve , Sensitivity and SpecificityABSTRACT
BACKGROUND: Antibodies to citrullinated proteins have been described in patients with RA and these appear to be the most specific markers of the disease. The objective of this study was to analyse the improvement in diagnostic accuracy of anti-cyclic citrullinated peptide autoantibodies and IgA rheumatoid factor in patients with clinical suspicion of RA and who were IgM rheumatoid factor-positive. Anti-CCP antibodies were measured with three different second-generation enzyme immunoassays. METHODS: We chose 133 serum samples with IgM RF levels greater than 20 IU/mL sent to our Laboratory from Specialized Care Units. Subsequently, patients were classified according to their clinical records. Eighty-seven had rheumatoid arthritis and 46 had other diseases. In all samples anti-CCP and IgA RF were measured by the corresponding ELISAs. RESULTS: Comparison of the three anti-CCP second-generation ELISAs revealed differences between them. Likewise, clinical performances in terms of sensitivity, specificity, and positive and negative likelihood ratios were different. In patients with IgM RF higher than 20 IU/mL, anti-CCP antibodies increased the clinical efficiency of IgM RF and offered better performance as compared with IgA RF. CONCLUSIONS: The use of anti-CCP antibodies affords good clinical efficiency and modifies the pre-test probability of the occurrence of RA in patients with IgM rheumatoid factor higher than 20 IU/mL.
Subject(s)
Autoantibodies/blood , Peptides, Cyclic/immunology , Rheumatoid Factor/blood , Arthritis, Rheumatoid/blood , Arthritis, Rheumatoid/diagnosis , Diagnosis, Differential , Enzyme-Linked Immunosorbent Assay , Female , Humans , Immunoglobulin A/blood , Immunoglobulin M/blood , Male , Middle Aged , Prospective Studies , Sensitivity and SpecificityABSTRACT
The evaluation of bone disease in multiple myeloma (MM) by conventional radiology has low reproducibility. In the last decade, several serum and urine biochemical parameters, for evaluation of bone turnover, have become available. The present study was designed to explore the value of six bone remodelation markers. It was studied in a series of 176 newly diagnosed patients with monoclonal gammopathies (107 MM and 69 monoclonal gammopathies of unknown significance (MGUS)). As control groups we used 25 patients with benign osteoporosis (BO) and 32 healthy individuals (HI). The bone markers analyzed included: bone resorption markers (BRM) (total pyridinoline, total deoxypyridinoline, free deoxypyridinoline and C-terminal telopeptide of collagen I) and bone formation markers (BFM) (bone alkaline phosphatase (bAP) and osteocalcin (OC)). Serum or urinary levels of BRM were significantly higher in MM patients than in MGUS patients, BO patients or HI (P < 0.001, respectively). BRM were higher in MM patients with lytic lesions. However, only C-terminal telopeptide discriminated MM patients without bone lesions from MGUS patients. BFM did not show significant differences in the aforementioned comparisons, although a trend toward higher values of OC and lower values of bAP in patients with early bone affectation was observed. Ratios BRM/BFM that contained bAP exhibited differences that were most significant between the MM group and other entities, as well as between the different MM subgroups. In fact, the ratios BRM/bAP provided discrimination between the MM subgroup without lyses and MGUS group (P < 0.01). BRM and BFM, especially the ratios, are useful in the evaluation of bone lesions in patients with monoclonal gammopathies.
