Rpp25 is a major target of autoantibodies to the Th/To complex as measured by a novel chemiluminescent assay.

INTRODUCTION: Autoantibodies to the Th/To antigen have been described in systemic sclerosis (SSc) and several proteins of the macromolecular Th/To complex have been reported to react with anti-Th/To antibodies. However, anti-Th/To has not been clinically utilized due to unavailability of commercial tests. The objective of the present study is to evaluate the newly developed ELISA and chemiluminescent immunoassay (CLIA) to measure autoantibodies to Rpp25 (a component of the Th/To complex) using immunoprecipitation (IP) as the reference method. METHODS: The first cohort consisted of 123 SSc patients including 7 anti-Th/To positive samples confirmed by IP. Additional seven anti-Th/To positive samples from non-SSc patients were also tested. For evaluation of the QUANTA Flash Rpp25 CLIA (research use only), 8 anti-Th/To IP positives, a cohort of 70 unselected SSc patients and sera from various disease controls (n = 357) and random healthy individuals (n = 10) were studied. RESULTS: Anti-Rpp25 antibodies determined by ELISA were found in 11/14 anti-Th/To IP positive but only in 1/156 (0.6%) negative samples resulting in a positive percent agreement of 78.6% (95% confidence interval [CI] 49.2, 95.3%) and a negative percent agreement of 99.4% (95% CI 96.4, 100.0%). To verify the results using a second method, 53 samples were tested by ELISA and CLIA for anti-Rpp25 reactivity and the results were highly correlated (rho = 0.71, 95% CI 0.56, 0.81; P < 0.0001). To define the cutoff of the CLIA, anti-Th/To IP positive and negative sera were tested using the anti-Rpp25 CLIA. At the cutoff selected by receiver operating characteristic (ROC) analysis 8/8 (100.0%) of the anti-Th/To positive sera but only 2/367 (0.5%) of the controls were positive for anti-Rpp25 antibodies. The positive and negative percent agreements were 100.0% (95% CI 63.1, 100.0%) and 99.5% (95% CI 98.0, 99.9%), respectively. In the disease cohorts 2/70 (2.9%) of the SSc patients were positive for anti-Rpp25 antibodies compared to 2/367 (0.5%) of the controls (P = 0.032). ROC analysis showed discrimination between SSc patients and controls with an area under the curve value of 0.732 (95% CI 0.655, 0.809). CONCLUSION: Rpp25 is a major target of autoantibodies to the Th/To autoantigen complex. Further studies are needed to evaluate the clinical utility of the new assays.

Usefulness of the BAST-24 smell and taste test in the study of diabetic patients: a new approach to the determination of renal function.

CONCLUSION: A reduction in the percentage of correct responses in the olfactory test indirectly indicated increased albuminuria and worse glomerular filtration rate (GFR) in diabetic patients. The olfactory function test is an indirect indicator of early microvascular complications in diabetic patients. OBJECTIVES: Diabetes mellitus is a highly prevalent disease that causes numerous complications. The aim of this study was to determine whether olfactory and taste sensations are related to renal failure in diabetic patients. METHODS: We studied 61 patients diagnosed with diabetes mellitus, mean age = 65.9 years (SD = 16.8), 54.1% male. We evaluated olfactory and taste sensations by determining the capacity of detection, identification and percentage of correct responses of the 29 components of the Barcelona Smell-taste Test-24 (BAST-24). We determined the relationship between these results and glycosylated haemoglobin (HbA1c), creatinine, albumin/creatinine, albuminuria and GFR (normal = GFR ≥ 60 ml/min/1.73 m(2); impaired renal function = GFR < 60 ml/min/1.73 m(2)). RESULTS: There was no significant relationship between HbA1c and olfactory and taste sensations. There was a significant relationship between the percentage of correct responses and albuminuria (p = 0.03) and between identification of odours through the olfactory nerve and GFR (p = 0.029), and the percentage of correct responses and GFR (p = 0.03). There was no significant relationship between taste and renal failure.