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Biomedical subjects

C J Walker

Publications and source records attributed to C J Walker.

61 records · Page 4Linked to original sources
PubMed1975

Hyperglucagonaemia in the surgical patient.

Twenty-one patients had serial samples of blood taken before, during, and after operation for the measurement of plasma glucagon, plasma insulin, and blood glucose concentrations. A significant rise in plasma glucagon level was noted during the operation. In contrast the plasma insulin concentration fell during the operation and rose in the postoperative period despite hyperglycaemia during and after the operation. These findings show that hyperglucagonaemia is a physiological consequence of a surgical operation and that the relationship of plasms glucagon to plasma insulin is complex.

Adolescent↗
PubMedDate not supplied

Human immunodeficiency virus 1 protease inhibitors in clinical practice: predictors of virological outcome.

OBJECTIVES: To ascertain whether prolonged suppression of viral replication can be achieved in clinical practice and to identify factors associated with virological outcome. DESIGN: Retrospective observational study. SETTING: University-affiliated human immunodeficiency virus (HIV) clinic in Cleveland, Ohio. PARTICIPANTS: Patients treated with regimens that included protease inhibitors between June 1995 and December 1997. We identified 366 patients; 310 had sufficient virological follow-up data to be included. MAIN OUTCOME MEASURE: Virological success was defined as plasma HIV-RNA levels lower than 400 copies/mL at the last clinic visit. Virological failure was subdivided according to the maximum degree of suppression of viral replication achieved. Multivariate analysis was performed to identify baseline factors associated with virological outcome. RESULTS: Virological success was achieved by 47% of patients at a median follow-up of 335 days. The median CD4+ cell count increase and HIV-RNA level decrease were 0.10x10(9)/L (100 cells/microL) and greater than 1.3 log10 in patients who achieved virological success, and 0.010x10(9)/L and 0.32 log10 for those who did not. In multivariate analysis the likelihood of virological success was diminished in women (P<.02) and in patients who missed 2 or more clinic visits in the prior year (P<.001), and decreased when the regimen was started earlier (P<.04). Patients with a lower nadir CD4+ cell count (P<.04) and higher peak plasma HIV-RNA levels (P<.001) also had a decreased likelihood of virological success. CONCLUSIONS: More than half the patients who started a regimen that included protease inhibitors in an academic clinical practice failed to achieve durable suppression of viral replication and also experienced a poorer immunologic outcome as determined by CD4+ cell count increase. Missed clinic visits, more advanced disease, and higher plasma HIV-RNA levels may predict failure.

Adolescent↗
PubMedDate not supplied

Developing optimal search strategies for detecting clinically sound studies in MEDLINE.

OBJECTIVE: To develop optimal MEDLINE search strategies for retrieving sound clinical studies of the etiology, prognosis, diagnosis, prevention, or treatment of disorders in adult general medicine. DESIGN: Analytic survey of operating characteristics of search strategies developed by computerized combinations of terms selected to detect studies meeting basic methodologic criteria for direct clinical use in adult general medicine. MEASURES: The sensitivities, specificities, precision, and accuracy of 134,264 unique combinations of search terms were determined by comparison with a manual review of all articles (the "gold standard") in ten internal medicine and general medicine journals for 1986 and 1991. RESULTS: Less than half of the studies of the topics of interest met basic criteria for scientific merit for testing clinical applications. Combinations of search terms reached peak sensitivities of 82% for sound studies of etiology, 92% for prognosis, 92% for diagnosis, and 99% for therapy in 1991. Compared with the best single terms, multiple terms increased sensitivity for sound studies by over 30% (absolute increase), but with some loss of specificity when sensitivity was maximized. For 1986, combinations reached peak sensitivities of 72% for etiology, 95% for prognosis, 86% for diagnosis, and 98% for therapy. When search terms were combined to maximize specificity, over 93% specificity was achieved for all purpose categories in both years. Compared with individual terms, combined terms achieved near-perfect specificity that was maintained with modest increases in sensitivity in all purpose categories except therapy. Increases in accuracy were achieved by combining terms for all purpose categories, with peak accuracies reaching over 90% for therapy in 1986 and 1991. CONCLUSIONS: The retrieval of studies of important clinical topics cited in MEDLINE can be substantially enhanced by selected combinations of indexing terms and textwords.

Diagnosis↗
PubMedDate not supplied

Performances of 27 MEDLINE systems tested by searches with clinical questions.

OBJECTIVE: To compare the performances of online and compact-disc (CD-ROM) versions of the National Library of Medicine's (NLM) MEDLINE database. DESIGN: Analytic survey. INTERVENTION: Clinical questions were drawn from 18 searches originally conducted spontaneously by clinicians from wards and clinics who had used Grateful Med Version 4.0. Clinicians' search strategies were translated to meet the specific requirements of 13 online and 14 CD-ROM MEDLINE systems. A senior librarian and vendors' representatives constructed independent searches from the clinicians' questions. The librarian and clinician searches were run through each system, in command mode for the librarian and menu mode for clinicians, when available. Vendor searches were run through the vendors' own systems only. MAIN MEASUREMENTS: Numbers of relevant and irrelevant citations retrieved, cost (for online systems only), and time. RESULTS: Systems varied substantially for all searches, and for librarian and clinician searches separately, with respect to the numbers of relevant and irrelevant citations retrieved (p < 0.001 for both) and the cost per relevant citation (p = 0.012), but not with respect to the time per search. Based on combined rankings for the highest number of relevant and the lowest number of irrelevant citations retrieved, the SilverPlatter CD-ROM MEDLINE clinical journal subset performed best for librarian searches, while the PaperChase online system worked best for clinician searches. For cost per relevant citation retrieved, Dialog's Knowledge Index performed best for both librarian and clinician searches. CONCLUSIONS: There were substantial differences in the performances of competing MEDLINE systems, and performance was affected by search strategy, which was conceived by a librarian or by clinicians.

Abstracting and Indexing↗