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Biomedical subjects

D L Kent

Publications and source records attributed to D L Kent.

29 records · Page 2Linked to original sources
PubMed1985

Improvements in data collection through physician use of a computer-based chemotherapy treatment consultant.

The impact of a computer-based data management system on the completeness of clinical trial data was studied before and after the system's introduction in an oncology clinic. Physicians use the system, termed ONCOCIN, to record data during patient visits and to receive advice about treatment and tests required by experimental cancer protocols. Although ONCOCIN does not force the user to enter all data expected by the protocol, after its introduction there was improvement in the recording frequency of such data. The percentage of expected physical findings recorded increased from 74% to 91% (P less than .05), toxicity history from less than 1% to 45% (P less than .01), general chemistry results from 36% to 82% (P less than .01), x-ray results from 44% to 73% (P less than .01), and physicians' assessments of overall disease activity and Karnofsky performance status from 73% to 91% (P less than .05). Analysis of the steps in data collection and their contribution to loss of data suggests that observations or test ordering which are dependent on the physician are most improved by the system. Furthermore, analysis of post-ONCOCIN visits when the system was unavailable suggests that the recording of physician-dependent data (physical findings and assessments of disease activity and performance status) is likely to revert to pre-ONCOCIN levels if the system is not used routinely. The results show that ONCOCIN can greatly enhance recovery of those data expected for chemotherapy protocol patients. The program's interaction with the physician is central to its effectiveness in data collection, especially for data that arise directly from the patient-physician encounter.

Antineoplastic Agents↗
PubMed1978

Histochemical, pharmacological and microspectrofluorometric analysis of new sites of serotonin localization in the rat hypothalamus.

Histopharmacological and microspectrofluorometric analysis was applied to the rat hypothalamus for the identification of serotonin. Neuronal perikarya, especially certain of those of the endocrinologically important arcuate nucleus, were seen to contain a yellow histofluorescence which possessed spectral characteristics consistent with the serotonin fluorophor. Serotonin was localized also within varicosities of various hypothalamic nuclei, as well as within an ependymally associated network of fibers. Pharmacological administration of the serotonin precursor, tryptophan, resulted in the identification of serotonin histofluorescence and spectra within hypothalamic neurons yielding evidence that these neurons possess the capacity to synthesize serotonin. These newly described cells may be of importance to the regulatin of hypothalamically mediated endocrine function due to their neuroanatomical placement in the medical basal hypothalamus.

Animals↗
PubMed1976

Localization of dopamine in the endocrine hypothalamus of the rat.

Microspectrofluorometry, fluorescence histochemistry and light and electron microscopic autoradiography have established the presence of sub-populations of neurons in the arcuate-periventricular region of the rat hypothalamus that sequester both radiolabeled dopamine and demonstrate formaldehyde-induced fluorescence. These characteristics are consistent with a catecholaminergic function. Selective sequestration of 3H-dopamine at the light and ultrastructural level is discussed in the context of an ultrashort loop autoregulatory mechanism for this neuronal population.

Animals↗
PubMedDate not supplied

Nasal hemangioma of pregnancy.

The nasal hemangioma of pregnancy is an uncommon but impressive cause of epistaxis. One patient with this condition recently treated at the Keller Army Hospital, West Point, exemplifies the problems encountered in the diagnosis and treatment of this puzzling disorder.

Adult↗
PubMedDate not supplied

Symptom severity and patients' values in the decision to perform a transurethral resection of the prostate.

To develop and validate a method to assess patients' subjective values for outcomes of surgical and nonsurgical management of benign prostatic hypertrophy (BPH), the authors studied 20 patients who had symptoms of BPH. Eight were scheduled for prostatic surgery and 12 were not. They conducted an interview, including a time-trade-off (TTO) exercise to elicit values for single and combined outcomes and questions about symptoms used to complete a symptom severity score. Expected gain and symptom severity were independent and significant (p less than 0.001 for both comparisons) determinants of whether surgery was scheduled, while the correlation between these two factors was limited (Spearman = 0.058, p = 0.004). Based on a decision analytic model incorporating TTO values, a high expected gain in quality from surgery was strongly related to whether surgery was scheduled (p = 0.002), and had a higher positive predictive value (0.86) than symptom severity score (0.73). This small study demonstrates the feasibility and validity of using value assessment in this setting and suggests that this approach can be useful to clinicians when counseling patients.

Aged↗
PubMedDate not supplied

Efficient scheduling of cystoscopies in monitoring for recurrent bladder cancer.

Proper timing for repeated evaluations is difficult to assess. The authors analyzed scheduling of cystoscopy to monitor patients for detection of recurrent bladder cancer assuming that 1) minimizing tumor detection delay helps prevent cancer morbidities; 2) only limited numbers of cystoscopies are available; 3) prediction of recurrence or progression to invasive cancer is uncertain; 4) future tumors recur according to a Poisson process. Assumptions 3 and 4 permit estimation of each patient's recurrence rate. Thus, patients may be compared according to their relative risks of future tumors. With these assumptions, nonlinear optimization theory was used to calculate monitoring schedules for a model practice. Given 5.4 available visits per week per 100 patients, cystoscopy was recommended in 9-11 weeks for high-risk patients and in 30-40 weeks for low-risk patients, depending on stages, grades, and numbers of previous tumors. In contrast, standard cystoscopy was recommended in 13, 26, or 52 weeks, depending only on time elapsed since last recurrence. The calculated schedule implied an average detection delay for potentially invasive tumors of eight weeks, while standard practice led to detection delays of 11 weeks (38% worse). These results suggest that inclusion of each patient's tumor history in an optimization approach may improve follow-up care for patients who have superficial bladder cancers. This approach is being evaluated in a larger clinical setting.

Appointments and Schedules↗
PubMedDate not supplied

Evaluation of nonlinear optimization for scheduling of follow-up cystoscopies to detect recurrent bladder cancer. The Bladder Cancer follow-up Group.

Standard recommendations for patients who have had superficial bladder cancer are inspection by cystoscopy quarterly for a year or two after tumor removal, then half-yearly and yearly. The authors assessed the potential for improvement in scheduling cystoscopies according to probabilistic optimization techniques. Eight hypothetical practices were created, based on retrospective analysis of 918 bladder-cancer-patient charts. Standard and alternative recommendations for the interval to next cystoscopy were compared. The alternatives were derived from patient-specific predictions of future tumor risks (based on the patient's prior recurrence rate and tumor stage and grade) and a nonlinear optimization approach to allocation of the same number of cystoscopies as were available for standard follow-up. The optimization proposed longer intervals between visits for low-risk patients and shorter intervals for high-risk patients. Overall, optimization reduced expected tumor detection delays by 30%, from 12.6 to 8.7 weeks. When optimization intervals were shorter than standard, cancer was found more often at subsequent cystoscopies (34% vs 27%, p less than 0.05), suggesting that the optimization was a better predictor of cancer recurrence. If reduction in tumor-detection delay is the goal of follow-up for recurrent cancers, then urologists can improve monitoring by using probabilistic optimization methods for scheduling cystoscopies. Further understanding of the accuracy of predictive models for bladder-cancer recurrence rates is desirable. Subsequently, the optimization method developed here may be tested prospectively.

Aftercare↗
PubMedDate not supplied

A model for planning optimal follow-up for outpatients on warfarin anticoagulation. Warfarin Optimal Outpatient Follow-up Study Group.

Patients taking warfarin for long-term anticoagulation require frequent clinic visits to monitor the prothrombin time ratio (PTR), a measure of blood clotting. A dynamic stochastic model using nonlinear optimization was developed to select follow-up visit intervals that minimize the overall costs of patient care. Assuming that fluctuations in a patient's PTR behave as a random diffusion process, future PTR fluctuations are unknown, except as revealed by past PTRs. To determine the incidence and costs of complications in relation to PTR, the authors reviewed the charts of 216 patients who had 719 patient-years of follow-up with 695 trivial, significant, life-threatening, or fatal complications. They modeled the relationship between costs of complications and deviation of the PTR from the therapeutic target as a fourth-order convex polynomial. The model is used to compute the interval to the next follow-up visit to minimize accumulated potential costs. Variables in the optimization are the cost of a monitoring visit and the expected costs of complications. The latter are derived from the current PTR, the variability of the patient's past PTR values, the number of past PTRs available, and the target PTR for the patient. No attempt is made to predict the level of the next PTR or suggest adjustments in the warfarin dose. Shorter follow-up is recommended for patients who have histories of large fluctuations in past PTRs and for patients with few prior PTR determinations. As visits accumulate, the patient's degree of variability can be estimated more accurately and visit intervals adjusted accordingly. The scheduling method balances costs to the health care system of monitoring each patient against the expected costs of complications. This approach has the potential to reduce the number of monitoring visits necessary for safe management of anticoagulated patients with stable PTRs and to improve control among unstable patients.

Aged↗
PubMedDate not supplied

Using treatment-tradeoff preferences to select diagnostic strategies: linking the ROC curve to threshold analysis.

Selection of optimal diagnostic strategies depends on the accuracy of diagnostic tests, the prevalence of disease, and the relative benefits and harms resulting from test/treatment choices. One can characterize diagnostic strategies according to their net benefit-to-harm ratios. Within the framework of expected-utility theory, the benefit-to-harm ratio is equivalent to the marginal tradeoff between erroneous and correct treatment choices. Consequently, a physician can identify his or her preferred strategy by asking the question: "How many additional treatment errors am I willing to make in order to treat one additional person correctly?" Family physicians were asked to indicate their lowest and highest acceptable tradeoff ratios in a survey about streptococcal pharyngitis. All 53 respondents indicated uncertainty about their preferred treatment-tradeoff ratios. For 58% of respondents, the midpoints of the acceptable range of tradeoff ratios corresponded to generally accepted diagnostic strategies: 1) test all or 2) treat if classic, test all others. In contrast, previously published patient utilities yield a treatment-tradeoff ratio that corresponds to the strategy of treating all cases. The analysis illustrates the linkage between the optimal operating point on a receiver operating characteristic (ROC) curve and the selection of a preferred diagnostic strategy based on treatment thresholds derived from benefit-to-harm ratios. The survey results indicate that physicians can respond directly to questions assessing their preferences for such treatment thresholds. Differences between patients and physicians have significant impacts on choices of test and treatment strategies.

Clinical Medicine↗