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R P Rodgers

Publications and source records attributed to R P Rodgers.

12 recordsLinked to original sources
PubMed1990

A critical reappraisal of the bleeding time.

Since its initial invention by the French worker Milian in 1901, the bleeding time has been put forward as a clinically useful test in three contexts: diagnosis (particularly of platelet disorders), prediction of clinically important bleeding, and assessment of the adequacy of various forms of therapy. Attempting a complete review of the published experience with this test, we assessed 862 articles. Original bleeding time data appeared in 664 of these articles, from which we tabulated 1083 distinct studies in humans. ROC analysis, which characterizes the sensitivity and specificity of the test, was applied in every instance in which published data were adequate (34 studies). ROCs from 27 studies of the bleeding time in association with aspirin ingestion reveal high variability in the ability of the bleeding time to detect aspirin intake, and provide evidence against claims that recently devised bleeding time methods have improved discriminatory ability based on improved reproducibility. Two ROCs from surgical studies, in which the bleeding time was used to try to predict abnormal bleeding, were statistically indistinguishable from that of a completely noninformative test. In ROCs from five studies of abnormal bleeding in uremia, the test performed approximately the same as the platelet count or hematocrit (taken singly); in one of these studies, prothrombin consumption was determined and was a better predictor of bleeding than bleeding time, hematocrit, or platelet count. In the settings of renal biopsy (one study) and massive transfusion (one study), data allowed estimation of predictive value: in no instance was there evidence that the bleeding time significantly altered a priori estimates (based on prevalence) of the risk of bleeding. Linear regression analysis was applied to data from 23 studies relating platelet count to bleeding time, to assess published claims that the bleeding time and platelet count follow a predictively useful linear relationship. In 22 of 23 instances, the inverse relationship between bleeding time and platelet count was associated with broad statistical scatter, making it impossible to predict precisely one variable given the other. The pathophysiology of an abnormal bleeding time remains poorly understood. The bleeding time is affected by a large number of diseases, drugs, physiologic factors, test conditions, and therapeutic actions, not all of them platelet-related. The test is likely to remain widely used for the diagnosis of inherited disorders of platelet function, such as von Willebrand's syndrome, despite the lack of clear criteria for its use in this context.(ABSTRACT TRUNCATED AT 400 WORDS)

Bleeding Time↗
PubMed1990

Persistent immune complexes and abnormal CD4/CD8 ratios in HIV infection.

We assessed the immunopathologic role of circulating immune complexes in human immunodeficiency virus infection by evaluating the data base and the serum bank of the San Francisco Men's Health Study, a longitudinal clinical and epidemiological investigation conducted since 1983. A group of 4,276 sera from 1,023 (including 811 homosexual/bisexual) men were tested for circulating immune complexes. We used a modification of the commercially available enzyme immunoassay test, based on monoclonal anti-C1q antibodies coupled to the solid phase, for capturing circulating immune complexes from the test serum, followed by detection of circulating immune complexes with either anti-IgG or with anti-IgM probes. Although persistent IgM and IgG circulating immune complexes were most frequently encountered in human immunodeficiency virus-seropositive homosexual/bisexual men, they were not an indicator of disease progression as assessed by abnormalities in the absolute numbers or ratios of CD4- and CD8-positive T cells, or clinical signs and symptoms of AIDS/ARC.

Acquired Immunodeficiency Syndrome↗
PubMed1989

(PLOT79): a comprehensive portable Fortran scientific line graphics system, as applied to biomedical research.

Scientific results are often most succinctly presented in graphical form. We describe a system for computer-generated scientific line graphics known as (PLOT79), named to commemorate the SIGGRAPH CORE graphics standard proposal of 1979. (PLOT79) is a widely used and actively evolving graphics system, written primarily in SFTRAN3, a structured procedural computer language which can be translated readily into Fortran. The package embodies concepts of sound software engineering, having been designed from the outset to be portable, maintainable and hardware-independent; much of the effort required to implement the system was directed toward the development of software engineering tools to ensure these goals. A modular design strategy has allowed a wide variety of graphics output devices to be supported. (PLOT79) has been installed under numerous operating systems, and software tools provided by UNIX have allowed particularly efficient installation and use of the system. Access to (PLOT79) is available through three avenues: (1) linking (PLOT79) routines with a user-written high-level program; (2) use of pre-written high-level applications programs which perform certain frequently-required tasks such as the plotting of simple two or three-dimensional data; or (3) the use of an interactive graphics command parser known as slides. (PLOT79) has proven popular among workers in the physical sciences and engineering both for its easy availability, openness (all source code is provided), and powerful capability. The system presents an equally important (though lesser known) resource for biomedical research, as demonstrated by examples from ongoing biomedical research projects. It also provides a focus for discussion of the practical limitations inherent in existing graphics standards and programming languages.

Computer Graphics↗
PubMed1988

Interrelations of lymphocyte subset values, human immunodeficiency virus antibodies, and HIV antigen levels of homosexual males in San Francisco.

Serum and leukocytes from a cohort of homosexual males were analyzed to determine the interrelationships of antibodies to human immunodeficiency virus (HIV), serum HIV antigen levels, and phenotypical differences in lymphocyte subpopulations of HIV antibody-positive (HIV Ab+) and HIV antibody-negative (HIV Ab-) homosexual males. Significant reductions were observed in the percentages of B lymphocytes, CD4+ and CD4+ kappa lambda- T lymphocytes and the CD4+/CD8+ ratios of HIV Ab+ homosexual males in comparison to HIV Ab- homosexual males. Significant increases were observed in the percentages of CD8+, CD8+ CD11b-, CD8+ kappa lambda-, CD8+ DR+, CD8+Leu7+, and Leu7+ lymphocytes of HIV Ab+ study subjects. Statistical analysis revealed that among the immunological variables tested, decreases in the CD4+/CD8+ ratio and in the percentage of CD4+ kappa lambda- lymphocytes showed the strongest associations with HIV-sero-positivity in asymptomatic homosexual males. Only 44 (16.5%) of 267 HIV Ab+ homosexual males had detectable levels of HIV antigen (HIV Ag) in their serum. The percentages of CD4+ or CD4+ kappa lambda- lymphocytes and the CD4+/CD8+ ratios of HIV Ab+ males differed significantly between HIV Ag-positive (HIV Ag+) and--negative (HIV Ag-) homosexual males. These variables, however, did not correlate well with HIV Ag levels,indicating that no clear associations can be drawn between levels of HIV antigen and lymphocyte subset abnormalities of HIV-infected individuals.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Influence of training and experience in fine-needle aspiration biopsy of breast. Receiver operating characteristics curve analysis.

In an effort to assess the influence of training and experience on the interpretation of fine-needle aspiration biopsy (FNAB) specimens, five observers with varying degrees of training and experience reviewed a series of 50 breast FNAB specimens. The cases selected were from the cytology registry of the University of California, San Francisco; all cases necessarily had histologic follow-up. By using receiver operating characteristics analysis, we were able to show that training and experience significantly influenced the interpretation of breast FNAB specimens. The two experts operated at a higher level of sensitivity and specificity than did three nonexperts. This study shows that training and experience are important in the interpretation of breast FNAB specimens. It also demonstrates the utility of receiver operating characteristics analysis in anatomic pathology.

Biopsy, Needle↗
PubMed1985

A complete system for barcode generation on the HP-41CX hand-held computer using a standard thermal printer.

One of the unique features of the HP-41C hand-held computer is its ability to read program code and alphanumeric data in the form of printed barcode. This greatly facilitates the dissemination of medical software and data used by this system. Initially, the ability to generate HP-41 barcode was restricted to a few centers in possession of specialized microcomputer equipment, and more recently to users able to either obtain a plotter read-only memory (ROM) module and HP7400 series plotter, or a dot-matrix impact printer, for which a special interface was then required. This paper presents a set of twenty programs which allows all nine types of HP-41C barcode to be generated using an HP-41CX, the commonly encountered 82162A thermal printer, an HP-IL ROM, and the plotter ROM. The package includes a number of input/output routines which are of general utility. Complete barcode listings, generated by the system itself, allow complete installation of the system without use of the keyboard. 'Synthetic programming' code permits the use of helpful non-standard characters in the display and allows that part of the system which is concerned with generating program barcode to run in extended memory, freeing main memory (RAM) to hold a large program. This system should make the generation of barcode much more widely available.

Abstracting and Indexing↗
PubMed1985

Guidelines for immunoassay data processing.

These guidelines outline the minimum requirements for a data-processing package to be used in the immunoassay laboratory. They include recommendations on hardware, software, and program design. We outline the statistical analyses that should be performed to obtain the analyte concentrations of unknown specimens and to ensure adequate monitoring of within- and between-assay errors of measurement.

Computers↗
PubMedDate not supplied

How much quality control is enough? A cost-effectiveness model for clinical laboratory quality control procedures (illustrated by its application to a ligand-assay-based screening program).

Quality assurance testing represents a substantial proportion of the clinical laboratory budget, but current guidelines are based on criteria that pertain to analytic error rather than to optimization of the cost-effectiveness of patient care. A general Bayesian mathematical model for the cost-effectiveness of assay quality control has been developed, and is demonstrated using previously published data. The cost-effectiveness of quality assurance as defined here depends upon the prevalence of disease, the shapes of the distributions of test results observed in the non-diseased and diseased populations, the decision limit selected for labeling results positive or negative, the costs and benefits associated with each of the possible therapeutic outcomes, the magnitude of random and systematic analytical errors, the statistical power of the quality control test in use, the costs associated with delays due to re-assay, and the proportion of total test cost attributable to quality control procedures. Given current clinical laboratory practice, much of this information will not be routinely available. The model combines these factors into a simple equation with three terms: one for the cost of the original and any required repeat laboratory analyses, one for the cost of delay entailed by the rejection of an assay batch, and one for the change in total costs consequent to rejection of erroneous assay results.

Clinical Laboratory Techniques↗