Clinical and pathologic findings in 2 siblings with congenital nephrotic syndrome.

We report the clinical and pathologic findings of 2 siblings affected with congenital nephrotic syndrome (CNS). The parents were a nonconsanguineous Mexican couple. The first sibling was born at term and developed proteinuria, hypoproteinemia, edema and ascites by its second month of life; he died septic at 6 months of age. The second sibling was diagnosed with congenital nephrosis during the second trimester of pregnancy. Prenatal demonstration of reno-placentomegaly can help in making the presumptive diagnosis of CNS in patients with high maternal serum and amniotic fluid AFP, normal acetylcholinesterase and normal karyotype. The pathologic findings of the kidneys of these siblings demonstrate that tubular microcysts are not critical to the disease process and are only the manifestation of a progressive disease in which the primary renal defect probably resides in a lack of integrity of the glomerular epithelial cells serving as filter.

Maintaining instrument quality while reducing items: application of Rasch analysis to a self-report of visual function.

While efficiency has been of concern in the measurement of health care outcomes, little attention has been devoted to methods that achieve efficient, shortened instruments that have good psychometric properties. The purpose of this study was to show how Rasch analysis could be used to reduce the number of items in an instrument while maintaining credible psychometric properties. This approach was applied to the Visual Function-14 (VF-14), a self-report of 14 vision-dependent activities, designed to measure the need for and outcomes of cataract surgery. An instrument which contained the VF-14 plus an additional 10 items that were developed for the study (VF-24) was administered to sixty-one patients (73.7+/-9.5 years) about to undergo extracapsular cataract removal at one of two surgical centers. Rasch analysis (BIGSTEPS) of the VF-14 showed a number of limitations to the original instrument, including: 1) unequal use of the five rating categories, 2) ceiling effect, 3) several other gaps where patient abilities did not match with item difficulties, and 4) sets of items that appeared redundant, (i.e., having the same calibration level). To resolve the first three of these problems, the rating scale was converted to a three-point scale and BIGSTEPS was run with all 24 items. (10 additional items added to the VF-14 designed to "fill in" the gaps). The conversion to a three-point scale and the increase in items resulted in some improvement in the matching of item difficulty to patient ability, as evidenced by a slight decrease in gaps. The addition of items resulted in improvements in person separation (2.55 to 2.99) and Cronbach's alpha (.83 to .91) but did not substantially reduce the ceiling effect and furthermore resulted in an increase in item redundancy. The final practical improvement undertaken was to reduce the number of items while attempting to maintain the psychometric qualities of the instrument as a whole. Three criteria were used in deciding to remove items: 1) high mean square, 2) low mean square and 3) items having similar calibrations. In addition, if an analysis showed that the removal of an item substantially decrease person separation, that item was retained for further analyses. Relative to the original VF-14, the resulting VF-10 showed less redundancy of items while person separation (2.20) and Cronbach's alpha (.89) remained relatively intact. The study demonstrates that Rasch analysis, while effective in elucidating the metrics of an original instrument, can also be useful in designing modifications of instruments that are both efficient and psychometrically sound.

Genetics and biology of human ovarian teratomas. II. Molecular analysis of origin of nondisjunction and gene-centromere mapping of chromosome I markers.

Chromosomal heteromorphisms and DNA polymorphisms have been utilized to identify the mechanisms that lead to formation of human ovarian teratomas and to construct a gene-centromere map of chromosome 1 by using those teratomas that arise by meiotic nondisjunction. Of 61 genetically informative ovarian teratomas, 21.3% arose by nondisjunction at meiosis I, and 39.3% arose by meiosis II nondisjunction. Eight polymorphic marker loci on chromosome 1p and one marker on 1q were used to estimate a gene-centromere map. The results show clear linkage of the most proximal 1p marker (NRAS) and the most proximal 1q marker (D1S61) to the centromere at a distance of 14 cM and 20 cM, respectively. Estimated gene-centromere distances suggest that, while recombination occurs normally in ovarian teratomas arising by meiosis II errors, ovarian teratomas arising by meiosis I nondisjunction have altered patterns of recombination. Furthermore, the estimated map demonstrates clear evidence of chiasma interference. Our results suggest that ovarian teratomas can provide a rapid method for mapping genes relative to the centromere.