Surveillance of CKD epidemiology in the US - a joint analysis of NHANES and KEEP.

Chronic Kidney Disease (CKD), is highly prevalent in the United States. Epidemiological systems for surveillance of CKD rely on data that are based solely on the NHANES survey, which does not include many patients with the most severe and less frequent forms of CKD. We investigated the feasibility of estimating CKD prevalence from the large-scale community disease detection Kidney Early Evaluation and Program (KEEP, n = 127,149). We adopted methodologies from the field of web surveys to address the self-selection bias inherent in KEEP. Primary outcomes studied were CKD Stage 3-5 (estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m2, and CKD Stage 4-5 (eGFR <30 mL/min/1.73 m2). The unweighted prevalence of Stage 4-5 CKD was higher in KEEP (1.00%, 95%CI: 0.94-1.05%) than in NHANES (0.51%, 95% CI: 0.43-0.59%). Application of a selection model that used  variables related to demographics, recruitment and socio-economic factors resulted in estimates similar to NHANES (0.55%, 95% CI: 0.50-0.60%). Weighted prevalence of Stages 3-5 CKD in KEEP was 6.45% (95% CI: 5.70-7.28%) compared to 6.73% (95% CI: 6.30-7.19%) for NHANES. Application of methodologies that address the self-selection bias in the KEEP program may allow the use of this large, geographically diverse dataset for CKD surveillance.

Genetic linkage analysis of hereditary arthro-ophthalmopathy (Stickler syndrome) and the type II procollagen gene.

Hereditary arthro-ophthalmopathy (AO), or Stickler syndrome, is a dominantly inherited disorder characterized by vitreo-retinal degeneration and frequently accompanied by epiphyseal dysplasia and premature degenerative joint disease. Three large families with AO were analyzed for clinical manifestations of the disease and for coinheritance of the genetic defect with RFLPs in the type II procollagen gene (COL2A1). Genetic linkage between AO and COL2A1 was demonstrated in the largest family, with a maximum LOD score of 3.52 at a recombination distance of zero. Data from a second family also supported linkage of AO and COL2A1, with a LOD score of 1.20 at a recombination distance of zero. These results are consistent with the conclusion that mutations in the COL2A1 gene are responsible for AO in these two families. In a third AO family, however, recombination between AO and COL2A1 occurred in at least one meiosis, and the data were inconclusive with respect to linkage.