Feasibility of keying data from screen-displayed facsimile images in an ongoing trial: the collaborative ocular melanoma study.

As part of an ongoing clinical trial, we conducted an experiment to assess the feasibility and to determine the reliability of data entry from a computer screen display of images of data collection forms transmitted by facsimile (fax) machines directly into a computer for paper forms designed without consideration of fax or image display requirements. Feasibility was assessed on the basis of accuracy and reliability of data entry and on operator satisfaction. During a 2-week period, half of the forms received at the Collaborative Ocular Melanoma Study (COMS) coordinating center were key-entered twice, using the paper forms as the source (paper source entry). The remaining forms were entered once using paper source and were later reentered using the screen display of images of the faxed forms as the source (image source entry). The latter group of forms, or 50% of all forms received, were entered a third time, using the image source entry. Two data entry operators participated in the experiment. Discrepancy rates between and within data entry operators were calculated for both modes of entry. A total of 50,861 keystrokes (28,095 items) across 1122 records were checked for consistency. The overall discrepancy rate associated with double paper source entry was approximately 21 per 10,000 keystrokes (20 per 10,000 items). Discrepancy rates associated with paper source versus image source entry (53 per 10,000 keystrokes [57 per 10,000 items]) and double image source entry (57 per 10,000 keystrokes [47 per 10,000 items]) were similar in magnitude. Image source entry of forms received by facsimile may provide an acceptable alternative to paper entry in ongoing multicenter clinical trials where the costs of converting existing forms and systems to automated data capture may be unacceptable. This experiment confirmed the feasibility of such an alternative and suggested that improved screen displays and changes in equipment to facilitate entry of data from the screen display may enhance accuracy of entries.

Genetic mapping of 21 genes on mouse chromosome 11 reveals disruptions in linkage conservation with human chromosome 5.

We report a high-resolution genetic map of 21 genes on the central region of mouse Chr 11. These genes were mapped by segregation analysis of more than 1650 meioses from three interspecific backcrosses. The order of these genes in mouse was compared to the previously established gene order in human. Eighteen of the 21 genes map to human Chr 5, and 2 of the genes define a proximal border for the region of homology between mouse Chr 11 and human Chr 17. Our results indicate a minimum of four rearrangements within the 10-cM region of synteny homology between mouse Chr 11 and human Chr 5. In addition, the linkage conservation is disrupted by groups of genes that map to mouse Chrs 13 and 18. These data demonstrate that large regions of conserved linkage can contain numerous chromosomal microrearrangements that have occurred since the divergence of mouse and human ancestors. Comparison of the mouse and human maps with data for other species provides an emerging picture of mammalian chromosome evolution.

Analysis of the vestigial tail mutation demonstrates that Wnt-3a gene dosage regulates mouse axial development.

Mice homozygous for the recessive mutation vestigial tail (vt), which arose spontaneously on Chromosome 11, exhibit vertebral abnormalities, including loss of caudal vertebrae leading to shortening of the tail. Wnt-3a, a member of the wingless family of secreted glycoproteins, maps to the same chromosome. Embryos homozygous for a null mutation in Wnt-3a (Wnt-3a(neo)) have a complete absence of tail bud development and are truncated rostral to the hindlimbs. Several lines of evidence reveal that vt is a hypomorphic allele of Wnt-3a. We show that Wnt-3a and vt cosegregate in a high-resolution backcross and fail to complement, suggesting that Wnt-3a(neo) and vt are allelic. Embryos heterozygous for both alleles have a phenotype intermediate between that of Wnt-3a(neo) and vt homozygotes, lacking a tail, but developing thoracic and a variable number of lumbar vertebrae. Although no gross alteration in the Wnt-3a gene was detected in vt mice and the Wnt-3a coding region was normal, Wnt-3a expression was markedly reduced in vt/vt embryos consistent with a regulatory mutation in Wnt-3a. Furthermore, the analysis of allelic combinations indicates that Wnt-3a is required throughout the period of tail bud development for caudal somitogenesis. Interestingly, increasing levels of Wnt-3a activity appear to be necessary for the formation of more posterior derivatives of the paraxial mesoderm.

The Markov process as a general method for nonparametric analysis of right-censored medical data.

The product limit method of Kaplan and Meier for estimating survival functions and the logrank test of Mantel are widely employed for analysis of longitudinal medical data. Developed for analysis of one-time events such as death, survival analysis is also commonly adapted to more complex states such as loss of vision or cancer remission by restricting analysis to first occurrences. The nonparametric discrete time nonhomogeneous Markov process is proposed as a better model for any applications of the latter type. This simple stochastic model allows for an arbitrary number of possible states and for transitions in any direction. Maximum likelihood estimators are easily computed for the stochastic model and are identical to the product-limit estimates in the special case represented by the Kaplan-Meier model. The logrank test extends to evaluation of differences between populations with respect to any specified transition.