PROBABILITY IMPUTATION REVISITED FOR PROGNOSTIC FACTOR STUDIES

The analysis of prognostic factor studies by Cox or logistic regression models is often impeded by missing covariate values. In 1990 Schemper and Smith recommended a conditional probability imputation technique (PIT) for the analysis of treatment studies which can be easily applied using standard software and which has been demonstrated to outperform the complete case and omission of covariates strategies. Recent research, however, showed that PIT cannot universally be recommended and it was concluded that model-based methods should be preferred. We agree with these conclusions but also think that there is enough empirical evidence to judge the performance of PIT to be satisfactory in typical prognostic factor studies. Furthermore, comparisons of PIT with multiple imputation in the same context did not indicate an advantage of the latter more involved technique. By means of an analysis of a prostate cancer data set various aspects of application of PIT are discussed, in particular that PIT permits direct comparability of marginal and partial effects analyses. We conclude that PIT continues to be an appropriate and attractive choice for analyses of prognostic factor studies. © 1997 by John Wiley & Sons, Ltd.     

CONTAMINATION OF PURIFIED PROSTATE-SPECIFIC ANTIGEN PREPARATIONS BY KALLIKREIN hK2

This paper ascertained the contamination by hK2 of two types of PSA preparation, that of Sensabaugh and Blake (J.Urol., 144: 1523, 1990) and that of Deperthes et al (J. Androl., 17: 659, 1996). In the first procedure, the free forms of hK2 co-migrated with PSA during the CM-Sephadex and the Sephacryl S-200 steps. By contrast, in the second procedure a very high proportion of hK2 was separated from PSA. In two different Sensabaugh and Blake procedures, the hK2 contamination per micro g. of PSA was found to be respectively 0.3 and 1.0 ng. We conclude that hK2 is a quantitatively minor contaminant of some PSA preparations. That contamination is probably of little consequence for PSA standardization but it could lead to erroneous conclusions in enzymatic studies of PSA.     

Transvenous Atrial Cardioversion Threshold in Patients with Implantable Cardioverter Defibrillator: Influence of Active Pectoral Can

Recent studies have shown that transvenous atrial cardioversion is feasible with lead configurations primarily designed for implantable cardioverter defibrillators (ICD). The purpose of this study was to examine the influence of an active pectoral ICD can on the atrial cardioversion threshold (ADFT). Forty consecutive patients received a transvenous single lead system (Endotak DSP 0125, CPI, St. Paul, MN, USA) in combination with a left subpectoral ICD (Ventak Mini, CPI) for treatment of malignant ventricular tachyarrhythmias. Patients were randomized into two groups: 21 received a Hot Can 1743 and 19 patients a Cold Can 1741. Step-down testing of the ventricular defibrillation threshold (VDFT) was performed intraoperatively and evaluation of the ADFT for induced atrial fibrillation (AF) at predischarge. After testing, each patient received a 2-J shock and was asked to quantify discomfort on a numerical scale ranging from 0 to 10. Both groups were comparable with regard to all clinical parameters studied. The mean VDFT in patients with a Hot Can device was significantly lower than in patients with a Cold Can (7.5 ± 2.3 J vs 9.8 ± 3.8 J; P < 0.03). The mean ADFT in the Hot Can group tended to be lower than in the group with Cold Cans (3.4 ± 1.4 J vs 4.5 ± 2.4 J; P = 0.07), and the proportion of patients in whom atrial cardioversion was accomplished at low energies (≤ 3 J) was higher in patients with active compared with patients with inactive pulse generators (57% vs 26%; P < 0.04). The mean discomfort reported after delivery of a 2-J shock was comparable in both groups (Hot Can 5.2 ± 1.9; Cold Can: 5.3 ± 2.1; P = NS). We conclude that the inclusion of an active left subpectoral can in the defibrillation vector of a ventricular ICD seems to reduce the energy requirements for atrial cardioversion without increasing the discomfort caused by low energy shocks.     

Discrimination of Sinus Rhythm, Atrial Flutter, and Atrial Fibrillation Using Bipolar Endocardial Signals

Discrimination of NSR, AFL, and AF. Introduction : Analysis of endocardial signals obtained from an electrode located in the right atrium as realized in newly designed dual chamber, implantable cardioverter defibrillators might be used to provide additional therapeutic options, such as overdrive pacing or low-energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Therefore, we developed a computer algorithm for discrimination of normal sinus rhythm (NSR), AFL, and AF that may lead to adequate differential therapy of atrial tachyarrhythmias in an automated mode.
Methods and Results : During an electrophysiologic study, bipolar endocardial signals from the high right atrium were obtained in 28 patients during sustained AFL or AF and after restoration of NSR. A total of 286 data segments of 5-second duration were recorded (NSR: 96, AFL: 86, AF: 104). Mean atrial cycle length (MCL), standard deviation of mean atrial cycle length (SDCK), and index of irregularity (IR). defined as the ratio between MCL and SDCL, were calculated for each data segment. A cutoff of 315 msec for MCL allowed discrimination of NSR from atrial tachyarrhythmias with 100% sensitivity and specificity. For discrimination of AF from AFI- by using SDCL, a cutoff value of 11.5 msec led to a sensitivity of 99% and a specificity of 90%. Best discrimination of AF from AFL was found for the criterion IR ≥ 7.5%, resulting in a sensitivity of 100% with a specificity of 95% for AF detection.
Conclusion : The investigated algorithm provides discrimination of NSR, AFL, and AF with high sensitivity and specificity. Incorporation of this algorithm in an implantable automated antitachycardia device may lead to adequate differential therapy in patients suffering from spontaneous episodes of AF and AFL.     

The Effect of Alcohol Intoxication on Primary and Secondary Processes in Male Social Drinkers

The acute effects of alcohol intoxication on cognitive style and on locus of control was investigated in an experimental setting. Sixty male subjects were randomly assigned to either an Alcohol, a Placebo, or a Control group. The alcohol dose was 1.0 ml of 100% alcohol/kg body weight. Subjects filled out a modified version of Rotter's locus of control scale and reported their perceptions to Street's Gestalt Completion Test. The latter test was scored in a standardized way for stimulus closeness, indicating a reality oriented and rational functioning, and stimulus distance, indicating a more primitive, irrational and pleasure oriented functioning. Alcohol made subjects less internally controlled and decreased the reality oriented functioning while the pleasure oriented functioning was not affected. Results were discussed in terms of pharmacological mechanisms, disinhibition, and creativity.     

SUTHERLAND ROTATABLE MICROSURGERY INSTRUMENTS

This article outlines the principle features of the Sutherland rotatable microsurgical instruments. Some of the developmental background is discussed. These instruments have lead to microsurgical advances in both the anterior and posterior segments of the eye. The more important applications are discussed.     

Free Amino-Acid Composition of Human Seminal Plasma in Different Andrological Diagnoses

Der Gehalt an f reien Aminosäuren im menschlichen Spermaplasma bei verschiedenen andrologischen Diagnosen
Der Gehalt an freien Aminosäuren des menschlichen Seminalplasmas wurde 30 min nach der Ejakulation bestimmt. Die Hauptbestandteile sind Serin, Threonin und Tyrosin. Ein Vergleich des Aminosäuregehaltes von vier andrologischen Diagnosen deutet auf eine Verknüpfung von freien Aminosäuren und Spermatozoen hin.