Scientific validation of two commercial pressure sensor systems for prosthetic socket fit.

The concept of measuring pressure at the interface between the stump and the prosthetic socket could provide valuable information in the process of prosthetic socket fabrication, modification, and fit. Two systems, the Rincoe Socket Fitting System (SFS) and Tekscan's F-Socket Pressure Measurement System, have been commercially designed for in situ interface pressure measurement over the past decade. Their use is not common in prosthetic practice, perhaps due to questions of cost effectiveness and the difficulties of interpreting the data. Another concern is the use of sensors for pressure measurements in areas of high contour and complex geometries such as the stump. Before these systems can be used in a clinical setting, it is necessary to determine the reliability and accuracy of each system. In order to assess the clinical validity of the Rincoe SFS and F-Socket systems, a series of trials was conducted to evaluate different aspects of sensor performance, namely; accuracy, hysteresis, drift and the effect of curvature. The sensors were subjected to tests in flatbed and custom-designed pressure vessels. Overall results indicated an accuracy error for the Rincoe SFS system of 25% (flatbed) and 33% (mould), with a corresponding 15% (flatbed) and 23% (mould) error in hysteresis, and 7% (flatbed) and 11% (mould) drift errors. The F-Socket system demonstrated an 8% (flatbed) and 11% (mould) accuracy errors, 42% (flatbed) and 24% (mould) hysteresis errors, and 12% (flatbed) and 33% (mould) drift errors. These findings indicate favourable results for the F-Socket Pressure Measurement System compared to the Rincoe Socket Fitting System with respect to its accuracy errors only. Nevertheless, it is the authors' belief that these systems are adequate in indicating areas of high pressure at the stump socket interface for clinical purposes, but both systems should be used with caution.

A longitudinal study of lymphocyte subsets in a cohort of cats naturally-infected with feline immunodeficiency virus.

Despite the potential of feline immunodeficiency virus (FIV) as an animal model for human immunodeficiency virus (HIV) studies, the long term effects of naturally-occurring infection have not been determined. HIV infection causes an ongoing deterioration in immune function which directly correlates with disease, in particular acquired immunodeficiency syndrome (AIDS). However, it is not known whether FIV-induced immunosuppression is progressive or related to the clinical condition. This study examined changes in lymphocyte subset numbers of serial samples, taken from cohorts of FIV-positive and FIV-negative cats over and 18-month period. FIV-positive cats were clinically staged as asymptomatic carriers (AC) or cats with AIDS-related complex (ARC), and FIV-negative cats matched and staged on the basis of similar diseases. During the course of the study, 4 FIV-positive cats developed AIDS, classed as the terminal stage of infection. There were no significant differences in the mean absolute numbers of any lymphocyte subset between the onset (t0) and the completion (t18) of the study. Similarly there were no significant changes in subset numbers during the 18 months preceding the development of AIDS. While the study period was brief and the sample sizes small, it is postulated that FIV infection in Australia may not necessarily cause progressive immunodeficiency and that FIV-induced immunosuppression (as measured by subset analysis) may not be well correlated with the clinical status of the infected cat.

The effect of intake procedures on performance in methadone maintenance.

The effect of assessment and intake procedures on the outcome of methadone maintenance treatment was investigated in a natural experiment in which a single methadone clinic admitted 89 patients by a rapid intake procedure, and 74 patients who had been on a waiting list and underwent formal assessment interviews. Outcome measures were frequency of illicit drug use as detected by urine tests, and risk of dropping out or being expelled from treatment. Subjects admitted after prolonged, formal assessment were more likely to be expelled, and were more than twice as likely to leave during the first 400 days of maintenance treatment (95% Cl relative risk 1.1 to 5.2). The odds of formally assessed subjects using heroin in the first 6 months of treatment were twice those of the rapid intake group (95% Cl odds ratio 1.5 to 2.2). The formal assessment process deterred half the initial applicants, yet seems to have either selected individuals with a worse prognosis or to have had a negative effect on in-treatment performance.

Clinic policy and retention in methadone maintenance.

Advantage was taken of a natural experiment to investigate the relationship of clinic objectives and procedures with retention in methadone maintenance. Assessment, maximum dose, and time in treatment data on 238 patients were summarized using Cox regression. While allowing for patient descriptors and maximum dose of methadone, those subjects assigned to a strongly abstinence-oriented program were 26% (95% C.I., 18 to 33%), 98% (66 to 137%), 213% (132 to 322%), and 393% (224 to 651%) more likely to leave treatment in the first, second, third, fourth 6 months of treatment, respectively, than those subjects assigned to a more laissez-faire program.

Prediction of outcome in acute renal failure by discriminant analysis of clinical variables.

To define factors of prognostic importance in patients with acute renal failure, we studied 23 clinical variables (including preexisting conditions, the acute clinical setting, and complications) by univariate and multivariate analysis in 148 patients. Ten variables contributed to discrimination in the overall analysis. Using a function derived by stepwise discriminant analysis, death could be predicted with a positive predictive value of 100% and a sensitivity of 58%. The performance of this discriminant score was validated in a subsequent group of 113 patients with a positive predictive value of 100% and a sensitivity of 26%. Thus, a fatal outcome of acute renal failure can be accurately predicted in a considerable proportion of patients by a weighted evaluation of clinical variables. The discriminant score may be useful in comparing the severity of illness among series of patients with acute renal failure.

On the receiving end--II. Linear analogue self-assessment (LASA) in evaluation of aspects of the quality of life of cancer patients receiving therapy.

Linear analogue self-assessment (LASA) scales were used to measure general well-being and specific factors (mood, pain, nausea and vomiting, appetite, breathlessness, physical activity) in patients receiving therapy for malignant melanoma, small cell bronchogenic carcinoma (SCBC) or ovarian cancer. Among the patients with SCBC and melanoma, high correlations were observed between LASA scores for general well-being, mood and appetite. There was a significant relationship between performance status and LASA scores for general well-being, pain and appetite. Among patients with ovarian cancer, there was a significant association between performance status and LASA scores for general well-being, breathlessness and physical activity. Objective response category was related to change in LASA scores for pain. Changes in LASA scores during treatment reflected increased morbidity during radiotherapy in patients also receiving chemotherapy for SCBC. The LASA technique provides a convenient method for the assessment of quality of life in patients receiving cancer therapy, and potentially allows comparison of patient perception of treatment-related morbidities.

Quantitative bone histology in the hypercalcemia of malignant disease.

Quantitative bone histology was studied in 23 patients with malignant hypercalcemia (MH) due to carcinoma (16) or immunoproliferative disease (7). Plasma calcium was 3.37 +/- 0.47 (mean +/- SD) mmol/liter. Bone resorbing surface (RS) was measured using a sensitive histochemical stain to identify osteoclasts. In the MH patients with carcinoma, the RS was 3.1 +/- 2.6% compared to 1.0 +/- 0.3% in controls (P less than 0.02). In the myeloma patients it was 2.3 +/- 1.7%, and in normocalcemic patients with malignant disease 0.8 +/- 1.1%. RS did not correlate with serum PTH, and several high RS values were associated with undetectable PTH. RS correlated with forming surface (FS) in MH patients (r = 0.44, P less than 0.05) and controls (r = 0.68, P less than 0.005), but there was a greater RS relative to FS in MH patients than in controls (P less than 0.005). "Excess" RS in the MH patients was calculated by subtracting the RS accounted for by the measured FS, using the relationship defined by the controls. Bone loss, as reflected in urinary calcium excretion, correlated weakly with excess RS (r = 0.44, P less than 0.05) but was high even when excess RS was zero. Thus, the histological findings do not account for the bone loss, and additional resorption around bone metastases is likely; the results of this study are consistent with a humoral substance produced by the malignant tissue causing generalized bone resorption in addition to bone dissolution around metastases.

Spline interpolation of demographic data.

There are many problems in demography involving the smoothing or interpolation of data. Usually a solution is obtained by fitting a polynomial or a suitable model curve. Often, however, fitting a spline proves to be a simple recourse. Splines, were invented nearly 30 years ago and have been shown to have desirable properties. Although spline functions are by no means unknown to demographers, no simple and direct explanation of their application exists. We hope to remedy this deficiency with this expository piece.

Higher-order diagnosis of two-way tables, illustrated on two sets of demographic empirical distributions.

Two-way tables of all kinds often require diagnosis, usually of the residuals after some simple fit such as row-PLUS-column or row-TIMES-column. The first step in diagnosis is likely to be either one-degree-of-freedom-for-non-additivity or a diagnositic plot (for which the former is the linear regression term). Not all diagnoses can be made at the first step. Some diagnostic plots appear like a diagonal cross, or, when such an appearance is not quite clear, become converted to oppositely tilted pictures when we look only at points with high fitted values and, separately, at those with low fitted values. Such behavior diagnoses a need for a more subtle re-expression than powers and logs, in our examples a need for a re-expression like plamda -(1 - p)lamda. The appearance and treatment of such diagnoses, in two examples, lead into the use of letter-value displays and the associated plots to study the character of non-normality, instances of the effect of the method of fitting on the shape of the distribution of residuals, and convenient algorithms for the iterative, recursive fitting of a variety of additive, multiplicative, and mixed additive-multiplicative models to any kind of two-way table, APL programs for which are appended.

The distribution by age of the frequency of first marriage in a female cohort.

PIP: The authors present 2 methods for the approximation of a representative schedule recording first marriage frequencies by age. Both treatments are mathematically complex. One method achieves a very close approximation with a simple closed form frequency function, which is the limiting distribution of the convolution of an infinite number of exponentially distributed components. The other method achieves an equal approximation by the convolution of a normal distribution of age of entry into a marriageable state and as few as 3 exponentially distributed delays. This latter convolution provides a feasible model of nuptiality, a model receiving surprising empirical support.^ieng