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Biomedical subjects

J R Feussner

Publications and source records attributed to J R Feussner.

115 records · Page 7Linked to original sources
PubMed1979

Arsenic-induced bone marrow toxicity: ultrastructural and electron-probe analysis.

A patient with severe arsenic poisoning that resulted in marked peripheral blood and bone marrow abnormalities, including megaloblastic erythropoiesis experienced many of the previously reported hematologic complications of arsenic poisoning: leukopenia, granulocytopenia, absolute eosinophilia, and profound anemia. In this study we report an ultrastructural and electron-probe analysis of the bone marrow. Although megaloblastic anemia associated with arsenic poisoning has been described rarely, the presence of arsenic in the local bone marrow milieu has not been demonstrated previously. The ultrastructural features of arsenic-induced bone marrow toxicity are similar to those described in other dyserythropoietic states and include marked nuclear aberrations involving shape, chromatin distribution, and nuclear envelope. Using the technique of energy-dispersive x-ray analysis (electron probe) we demonstrated arsenic in bone marrow spicules; this supports the contention that arsenic can cause megaloblastic anemia. We suggest that this technique may be a useful tool in further studies that attempt to explore the mechanism of arsenic-induced hematologic toxicity. Finally, we suggest that arsenic has a direct toxic effect on DNA synthesis that results in marked disturbances of nuclear division. We recommend that the most appropriate screening procedure to evaluate possible arsenic poisoning is tissue arsenic measurements (hair and nails) rather than 24-hr urinary measurements.

Adult↗
PubMedDate not supplied

Quantitating bedside diagnosis: clinical evaluation of ascites.

The authors prospectively evaluated the operating characteristics of the history and physical examination for ascites in a broad spectrum of hospitalized patients. The overall clinical evaluation produced a positive likelihood ratio = 37.7-83.3 when suggestive of ascites, a likelihood ratio = 2.23-3.42 when intermediate, and a negative likelihood ratio = 0.77-0.90 when not suggestive of ascites. Patients' perceptions of increased abdominal girth (positive likelihood ratio = 4.16) or recent weight gain (positive likelihood ratio = 3.20) increased the likelihood of ascites. The absence of subjective ankle swelling (negative likelihood ratio = 0.10) or increased abdominal girth (negative likelihood ratio = 0.17) decreased the likelihood of ascites. The positive likelihood ratios for a fluid wave = 9.6 and shifting dullness = 5.76 favored ascites, while the absence of bulging flanks (negative likelihood ratio = 0.12) or peripheral edema (negative likelihood ratio = 0.17) favored ascites the least. Thus, a routine history and physical examination are quantitatively useful in the clinical evaluation of ascites.

Ascites↗
PubMedDate not supplied

Observer variability in the pulmonary examination.

Observer variability in the pulmonary examination was assessed by having four blindfolded observers (two medical students and two pulmonary physicians) twice examine 31 patients with abnormal pulmonary findings. Examiners were consistent in the repetitive detection of pulmonary abnormalities in 74-89% of the examinations; conversely, 11-26% of the time they disagreed with themselves. Although pulmonary specialists recorded fewer (55% of observations) abnormal findings than did medical students (74%), they were significantly (p = 0.008) less self-consistent than were the students. There was no clear trend in agreement between examiners (kappa = 0.20-0.49). Each examiner's findings were compared with those of physicians specially trained in pulmonary examination. Dichotomous variables (wheezes, crackles, rubs) were more reliably detected (kappa = 0.30-0.70) than graded variables (tympany, dullness, breath sound intensity), where kappa = 0.16-0.43. The authors suggest that dichotomous variables deserve greatest clinical reliance; that time in training, alone, does not improve clinical performance; and that there is a disconcertingly large amount of inter- and intraobserver disagreement in this fundamental clinical task.

Humans↗
PubMedDate not supplied

Intermediate, indeterminate, and uninterpretable diagnostic test results.

Diagnostic tests do not always yield positive or negative results; sometimes the results are intermediate, indeterminate, or uninterpretable. No consensus exists for the incorporation of such results into data assessment. Conventional Bayesian analysis leads investigators to either exclude patients with non-positive, non-negative results from their studies or categorize such results into inappropriate cells of the standard four-cell decision matrix. The authors propose a standardized method for reporting results in studies dealing with diagnostic test use and discuss how researchers should expand the four-cell matrix to six cells when non-positive, non-negative results occur. They suggest that the six-cell matrix with new operational definitions of sensitivity, specificity, likelihood ratios, and test yield should be adopted routinely. In addition, they define the different types of non-positive, non-negative results and demonstrate how clinicians can use tree-structured decision analysis from the six-cell matrix. While their method does not solve all problems posed by non-positive, non-negative results, it does suggest a standard method for reporting these results and utilizing all the data in decision making.

Bayes Theorem↗
PubMedDate not supplied

A Bayesian method for evaluating medical test operating characteristics when some patients' conditions fail to be diagnosed by the reference standard.

The evaluation of a diagnostic test when the reference standard fails to establish a diagnosis in some patients is a common and difficult analytical problem. Conventional operating characteristics, derived from a 2 x 2 matrix, require that tests have only positive or negative results, and that disease status be designated definitively as present or absent. Results can be displayed in a 2 x 3 matrix, with an additional column for undiagnosed patients, when it is not possible always to ascertain the disease status definitively. The authors approach this problem using a Bayesian method for evaluating the 2 x 3 matrix in which test operating characteristics are described by a joint probability density function. They show that one can derive this joint probability density function of sensitivity and specificity empirically by applying a sampling algorithm. The three-dimensional histogram resulting from this sampling procedure approximates the true joint probability density function for sensitivity and specificity. Using a clinical example, the authors illustrate the method and demonstrate that the joint probability density function for sensitivity and specificity can be influenced by assumptions used to interpret test results in undiagnosed patients. This Bayesian method represents a flexible and practical solution to the problem of evaluating test sensitivity and specificity when the study group includes patients whose disease could not be diagnosed by the reference standard.

Algorithms↗
PubMedDate not supplied

The cost-effectiveness of a clinical pharmacist intervention among elderly outpatients.

We estimated the cost and cost-effectiveness of a clinical pharmacist intervention known to improve the appropriateness of drug prescribing. Elderly veteran outpatients prescribed at least five drugs were randomized to an intervention (105 patients) or control (103) group and followed for 1 year. The intervention pharmacist provided advice to patients and their physicians during all general medicine visits. Mean fixed and variable costs/intervention patient were $36 and $84, respectively Health services use and costs were comparable between groups. Intervention costs ranged from $7.50-30/patient/unit change in drug appropriateness. The cost to improve the appropriateness of drug prescribing is thus relatively low.

Aged↗