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Background: The aim of the study was to describe automated immunoassays for autoantibodies to homocitrulline or citrulline containing telopeptides of type I and II collagen in various disease categories in an early arthritis series., Methods: Serum samples were collected from 142 patients over 16 years of age with newly diagnosed inflammatory joint disease. All samples were analyzed with an automated inhibition chemiluminescence immunoassay (CLIA) using four different peptide pairs, each consisting of a biotinylated antigen and an inhibiting peptide. Assays were performed with an IDS-iSYS analyzer. Autoantibodies binding to homocitrulline and citrulline containing C-telopeptides of type I (HTELO-I, TELO-I) and type II collagens (HTELO-II, TELO-II) were analyzed., Results: The mean ratio of HTELO-I inhibition in seropositive and seronegative rheumatoid arthritis (RA) was 3.07 (95% CI 1.41-11.60), p=0.003, and in seropositive and seronegative undifferentiated arthritis (UA) 4.90 (1.85-14.49), p<0.001. The respective mean ratios in seropositive and seronegative RA and UA were in TELO-I 8.72 (3.68-58.01), p<0.001 and 3.13 (1.49-6.16), p=0.008, in HTELO-II 7.57 (3.18-56.60), p<0.001 and 2.97 (1.23-6.69), p=0.037, and in TELO-II 3.01 (1.30-9.51), p=0.002 and 3.64 (1.86-7.65), p=0.008. In reactive arthritis, ankylosing spondylitis, psoriatic arthritis and unspecified spondyloarthritis the inhibition levels were similar to those observed in seronegative RA or UA., Conclusions: Autoantibodies binding to homocitrulline or citrulline containing telopeptides of type I and II collagen did not differ significantly. They were highest among patients with seropositive disease and they differentiated seropositive and seronegative arthritis.

Background: Comparing four fully automated 25-OH-D immunoassays to a commercially available liquid chromatography-tandem mass spectrometry (LC-MS/MS) method with human serum samples from Finnish population., Methods: 400 samples were analyzed with the Liaison Total Vitamin D, the IDS-iSYS 25-Hydroxy Vitamin D, the ARCHITECT 25-OH Vitamin D, the ADVIA Centaur Vitamin D Total, and a commercially available LC-MS/MS 25-OH D (PerkinElmer) method., Results: The Liaison method mean value (95% confidence intervals) was 65.6 nmol/L (62.6 - 68.6); the IDS-iSYS mean was 70.3 nmol/L (67.4 - 73.1); the ARCHITECT mean was 69.0 nmol/L (65.5 - 72.5); ADVIA Centaur mean was 71.6 nmol/L (68.9 - 74.3), and the LC-MS/MS mean was 82.8 nmol/L (79.4 - 86.2). The regression coefficients (r) between the LC-MS/MS and immunoassays were 0.650 for Liaison, 0.757 for IDS-iSYS, 0.721 for ARCHITECT and 0.684 for ADVIA Centaur. With the Passing-Bablok analysis, none of the immunoassays gave results equivalent to LC-MS/MS. Two of the four automated 25-OH-vitamin D assays (IDS-iSYS, ADVIA Centaur) were overall in good clinical agreement with LC-MS/MS, even though the results obtained with all compared methods were not equivalent., Conclusions: In conclusion, in routine clinical laboratory both immunoassays and LC-MS/MS are useful for measuring 25-OH-vitamin D provided that these methods are correctly standardized and especially sample pretreatment is carefully performed.

Background: IDS-iSYS intact parathyroid hormone (iPTH) assay was evaluated. Two automated second generation assays for measuring iPTH were also compared to each other. The compared assays detected PTH fragments 1-84 and 5-84., Methods: The iPTH was analyzed from controls (n = 88) and samples of patients with chronic kidney disease (CKD) (n = 100) on the IDS-iSYS (iSYS) and Siemens ADVIA Centaur (Centaur) immunoanalyzers., Results: In controls, the iSYS method mean value (95% CI ranges) was 37.1 pg/mL (34.3 to 39.9) and the Centaur was 39.3 pg/mL (36.3 to 42.3). The regression coefficient (r) between the iSYS and the Centaur was 0.850 in controls. Correspondingly, in CKD patients the iSYS method mean value (95% CI ranges) was 183.3 pg/mL (154.3 to 212.4) and the Centaur was 199.7 pg/mL (170.4 to 229.0). In CKD patients the regression coefficient (r) between the iSYS and the Centaur was 0.964. With Passing-Bablok analysis, the automated iPTH methods gave clinically similar results in controls and in CKD patients. However, in the difference blots, the iSYS gave lower concentrations when the mean concentration increased., Conclusions: The IDS-iSYS iPTH assay is precise. The iSYS concentrations of iPTH were clinically similar with those determined by Centaur.

Background: Comparing two fully automated 25-OH-D immunoassays with a validated liquid chromatography isotope dilution tandem mass spectrometry (LC-IDMS/MS) method in human serum samples., Methods: 180 samples were analyzed with the Liaison TOTAL Vitamin D, the IDS-iSYS 25-Hydroxy Vitamin D, and a validated LC-IDMS/MS 25-OH D method., Results: The Liaison method mean +/- standard deviation (SD) was 64.3 +/- 23.5 nmol/L; the IDS-iSYS 70.1 +/- 27.0 nmol/L, and the LC-IDMS/MS 68.9 +/- 24.6 nmol/L. The correlation coefficient (r) between the Liaison and LC-IDMS/MS was 0.723, and the r between the IDS-iSYS and LC-IDMS/MS was 0.799. When the samples were grouped by females and males, the r between the Liaison and LC-IDMS/MS was 0.680 and 0.846, being 0.781 and 0.863 between the IDS-iSYS and LC-IDMS/MS, respectively. With the Passing-Bablok analysis, only the IDS-iSYS gave equivalent results to LC-IDMS/MS., Conclusions: The automated 25-OH-D immunoassays were in clinically good overall agreement with the LC-IDMS/MS method.

We developed sensitive assay methods for autoantibodies recognizing the citrullinated synthetic peptides derived from type I and type II collagens in patients with rheumatoid arthritis (RA). These peptides were tested with the chemiluminescence method (Nichols Advantage System). In 44 RA patients out of 120, the sera showed increased binding of citrullinated synthetic C-telopeptide derived from the alpha1 chain of type I collagen (p=0.003 compared to controls). For a corresponding C-telopeptide pair from the alpha1 chain of type II collagen, 35 patient sera bound the citrullinated peptide more strongly than the arginine peptide, but the difference compared to the controls was not significant (p=0.074). Correlation between the two carboxy-telopeptides was r=0.473 (p<0.001). The anti-CCP assay (antibodies against citrullinated filaggrin sequence-derived peptides) was positive in 59% of our RA patients. There was no relationship between the anti-CCP results and the antibodies against collagen C-telopeptides, but both are increased in RA patients. We demonstrated autoantibodies in RA patients that bound citrullinated C-telopeptides derived from type I and type II collagen antigens. The peptide sequences detected (-YYXA and -YMXA) were different from that based on the cyclic filaggrin antigen (-STXG-, where X represents citrulline).