Recovery of the Baseline Incidence Density in Censored Time-to-Event Analysis

Abstract Time-to-event analyses are often concerned with the effects of explanatory factors on the underlying incidence density, but since there is no intrinsic interest in the form of the incidence density itself, a proportional hazards model is used. When part of the purpose of the analysis is to use actual cumulative incidence for simulation, or for providing informative visual displays of the results, an estimate of the baseline incidence density is required. The usual method for estimating the baseline hazards in Cox’s proportional hazards analysis yields values that are of little use, and furthermore no standard deviations of the estimates (SDEs) are available. In this article we present an alternative approach to recovering an estimate of the baseline incidence density that yields smooth estimates as well as smooth estimates of SDEs. We illustrate the method on a large dataset of inter-visit times for individuals in a diabetes registry, and indicate how it can be used to incorporate different baseline incidence densities in the analysis of different subgroups. Keywords: proportional hazards, exponential regression, survival analysis, diabete

Augmentation of Propensity Scores for Medical Records-based Research

Therapeutic research based on electronic medical records suffers from the possibility of various kinds of confounding. Over the past 30 years, propensity scores have increasingly been used to try to reduce this possibility. In this article a gap is identified in the propensity score methodology, and it is proposed to augment traditional treatment-propensity scores with outcome-propensity scores, thereby removing all other aspects of common causes from the analysis of treatment effects

The Linkset Model for 2^n Contingency Tables

Abstract The linkset model is defined for parametrizing the general 2^n contingency table. The linkset parameters are designed to represent latent influences that promote the co-occurrences of binary events beyond that explained by chance. Linkages involving 2 through n binary variables are included in this parametrization. The intent of this process is to elucidate the patterns of linkage, no matter how complex they might be, rather than to fit simplifying models. The relationship between linkset parameters and the natural parameters for a 2n table are derived, and large sample inference methods are provided. Examples are given from medical diagnostics, survival from the Titanic sinking, and employment discrimination in Chicago

Adynamia episodica hereditaria with myotonia: A non-inactivating sodium current and the effect of extracellular pH

To study the mechanism of periodic paralysis, we investigated the properties of intact muscle fibers biopsied from a patient who had adynamia episodica hereditaria with electromyographic signs of myotonia. When the potassium concentration in the extracellular medium, [K]e, was 3.5 mmol/l, force of contraction, membrane resting potential, and intracellular sodium activity were normal, but depolarizing voltage clamp steps revealed the existence of an abnormal inward current. This current was activated at membrane potentials less negative than -80 mV, reached a maximum within 50 msec, and was not inactivated with time. The inward current was completely and reversibly blocked by tetrodotoxin, which indicates that it was carried by sodium ions. In a solution containing 9 mmol/l potassium, normal muscle would depolarize to -63 mV and yet be capable of developing full tetanic force upon stimulation. The muscle from the patient depolarized to -57 mV and became inexcitable, i.e., it was paralyzed. A contracture did not develop. Lowering of the extracellular pH did not influence the resting potential, but it effectively antagonized or prevented the paralytic effect of high [K]e by changing the inactivation characteristics of the sodium channels. Hydrochlorothiazide, which had a therapeutic effect on the patient, did not prevent paralysis in vitro. An abnormal rise of the intracellular sodium activity was recorded when the extracellular potassium concentration was raised to 10 mmol/l

Pseudomyxoma peritonei

The subject of Ovarian Tumours and their effects is an exceedingly interesting and important one, especially in view of the efforts that are now being spade to elucidate their origin and nature.I have abstracted and epitomised the whole of the literature on Pseudomyxoma Peritonea, and present it here in what I believe to be the only complete and up-to -date account of the subject, in the hope that it may throw some light on this obscure condition, and serve as a foundation for future study.I wish to draw attention to the Histological aspect of my subject, as it in of great importance, especially mentioning in this connection the works of WERTH, WESTPHALEN, STRASSMAIN, GREENFIELD, and others.For the more complete elucidation of the Histology of Pseudomyxoma Peritonea, I have endeavoured to give in full detail the separate accounts of these authorities, adding as opportunities presented themselves, deductions and abstracts of my own, together with a complete original Histological research, carried on by myself, and illustrated by a series of Microphotographs

Prevalence of Disorders Recorded in Dogs Attending Primary-Care Veterinary Practices in England

Purebred dog health is thought to be compromised by an increasing occurence of inherited diseases but inadequate prevalence data on common disorders have hampered efforts to prioritise health reforms. Analysis of primary veterinary practice clinical data has been proposed for reliable estimation of disorder prevalence in dogs. Electronic patient record (EPR) data were collected on 148,741 dogs attending 93 clinics across central and south-eastern England. Analysis in detail of a random sample of EPRs relating to 3,884 dogs from 89 clinics identified the most frequently recorded disorders as otitis externa (prevalence 10.2%, 95% CI: 9.1-11.3), periodontal disease (9.3%, 95% CI: 8.3-10.3) and anal sac impaction (7.1%, 95% CI: 6.1-8.1). Using syndromic classification, the most prevalent body location affected was the head-and-neck (32.8%, 95% CI: 30.7-34.9), the most prevalent organ system affected was the integument (36.3%, 95% CI: 33.9-38.6) and the most prevalent pathophysiologic process diagnosed was inflammation (32.1%, 95% CI: 29.8-34.3). Among the twenty most-frequently recorded disorders, purebred dogs had a significantly higher prevalence compared with crossbreds for three: otitis externa (P = 0.001), obesity (P = 0.006) and skin mass lesion (P = 0.033), and popular breeds differed significantly from each other in their prevalence for five: periodontal disease (P = 0.002), overgrown nails (P = 0.004), degenerative joint disease (P = 0.005), obesity (P = 0.001) and lipoma (P = 0.003). These results fill a crucial data gap in disorder prevalence information and assist with disorder prioritisation. The results suggest that, for maximal impact, breeding reforms should target commonly-diagnosed complex disorders that are amenable to genetic improvement and should place special focus on at-risk breeds. Future studies evaluating disorder severity and duration will augment the usefulness of the disorder prevalence information reported herein