HMO marketing and selection bias: are TEFRA HMOs skimming?

The research evidence indicates that health maintenance organizations (HMOs) participating in the Tax Equity and Fiscal Responsibility Act of 1982 (TEFRA) At-Risk Program tend to experience favorable selection. Although favorable selection might result from patient decisions, a common conjecture is that it can be induced by HMOs through their marketing activities. The purpose of this study is to examine the relationship between HMO marketing strategies and selection bias in TEFRA At-Risk HMOs. A purposive sample of 22 HMOs that were actively marketing their TEFRA programs was selected and data on organizational characteristics, market area characteristics, and HMO marketing decisions were collected. To measure selection bias in these HMOs, the functional health status of approximately 300 enrollees in each HMO was compared to that of 300 non-enrolling beneficiaries in the same area. Three dependent variables, reflecting selection bias at the mean, the low health tail, and the high health tail of the health status distribution were created. Weighted least squares regressions were then used to identify relationships between marketing elements and selection bias. Subject to the statistical limitations of the study, our conclusion is that it is doubtful that HMO marketing decisions are responsible for the prevalence of favorable selection in HMO enrollment. It also appears unlikely that HMOs were differentially targeting healthy and unhealthy segments of the Medicare market.

The unique Duvernoy's secretion of the brown tree snake (Boiga irregularis).

Recently, bites by the colubrid Boiga irregularis (brown tree snake) in infants and young children on Guam have produced severe systemic reactions which bear some resemblance to classical manifestations of neurotoxic venom poisoning. This study demonstrates that the Duvernoy's secretion which elicits these reactions is a remarkably simple venom secretion with comparatively low toxicity and generally weak enzymatic activity. The intravenous LD50 for Swiss-Webster mice was approximately 80 mg/kg; significant neurotoxic manifestations were not observed in mouse trials. Deaths of lethally challenged mice occurred within minutes of injection, and appeared to result from cardiopulmonary crises. Duvernoy's secretion yields, protein content, enzyme activities, electrophoretic data and toxicity characteristics of the secretion are presented.

Some effects and properties of Duvernoy's gland secretion from Hypsiglena torquata texana (Texas night snake).

The Texas night snake (Hypsiglena torquata texana), a small opisthoglyphic colubrid snake, produces a Duvernoy's secretion which has a relatively low lethal toxicity for mice, but produces pain, hemorrhage, and oedema at the site of injection. The subcutaneous LD50 of Hypsiglena torquata texana Duvernoy's secretion in Swiss-Webster mice was 26 mg/kg. Local hemorrhaging occurred at doses as low as 2.0 micrograms/mouse, while marked hemorrhage and oedema resulted at doses greater than 200 micrograms/mouse. The dry secretion contained 77% protein, and SDS-PAGE electrophoresis revealed the presence of seven major proteinaceous components.

Necrotic arachnidism in the northwest United States and its probable relationship to Tegenaria agrestis (Walckenaer) spiders.

Necrotic spider bites in the states of Washington, Oregon and Idaho, U.S.A., have become increasingly frequent during the past decade. The great majority of cases seen by physicians are tentatively diagnosed as 'brown recluse' spider bite on the basis of clinical manifestations. However, investigation of over 30 such cases from several northwest localities has revealed that Tegenaria agrestis, a spider introduced into the northwest U.S. from Europe, is almost invariably found at the locality where the bite probably occurred. Necrotic arachnidism was seen only in areas where populations of Tegenaria agrestis spiders were well established and did not occur where Tegenaria agrestis was absent. The geographical spread of Tegenaria agrestis spiders parallels the appearance of necrotic arachnidism in several areas. Evaluation of some individual cases strongly implicates Tegenaria agrestis as the responsible organism and Tegenaria agrestis is likely responsible for the majority of 'brown recluse' spider bites seen in the northwest U.S. Tegenaria agrestis should now be considered a species of clinical significance capable of producing marked dermal lesions and, not infrequently, severe toxicosis in humans. Case histories are presented and manifestations of poisoning are described.

Envenomation by Tegenaria agrestis (Walckenaer) spiders in rabbits.

Preliminary studies in rabbits demonstrate that envenomation by the male Tegenaria agrestis spider produces a slowly developing dermal lesion, which exhibits gravitational drift and extensive subcutaneous hemorrhaging. Petechial hemorrhages were present on the lungs, liver and kidneys of rabbits bitten by male Tegenaria agrestis. Female Tegenaria agrestis trials in rabbits produced no significant effects in New Zealand white rabbits, but produced dermal lesions in the California giant strain.

Preliminary studies on the venom of the Chinese snake Azemiops feae, Boulenger (Fea's viper).

Fea's viper (Azemiops feae) produces a venom which is highly toxic to mice when injected by the s.c. or i.v. routes. The i.v. LD50 of Azemiops venom for Swiss-Webster laboratory mice is 0.52 mg/kg. Azemiops venom produces no hemorrhagic activity in mice or rabbits. Immunodiffusion indicates that some fractions of Azemiops venom are antigenically related to viperid, elapid and crotalid venoms. SDS-PAGE electrophoresis reveals that this venom contains as many as 22 proteinaceous components.

Envenomation following the bite of a wandering garter snake (Thamnophis elegans vagrans).

Following a prolonged bite by a large specimen of the wandering garter snake (Thamnophis elegans vagrans), symptoms of envenomation rapidly developed. Swelling, edema, pain, and localized hemorrhaging occurred but without the subsequent onset of systemic manifestations. The bite recipient was carefully examined and the evolution of poisoning monitored. Depending upon duration of the bite and inclination of the snake, members of this species are capable of occasionally causing mild envenomation in humans, inducing localized poisoning not unlike that seen following bites by small Crotalidae (pit vipers).

Envenomation by a juvenile Malayan pit viper (Agkistrodon rhodostoma).

Following an accidental bite inflicted by a juvenile Malayan pit viper (Agkistrodon rhodostoma), the progress of envenomation was carefully monitored and subsequent laboratory work performed to determine the amount and quality of venom injected. Even a very small amount of venom from this species is capable of inducing noticeable local symptoms including edema, subcutaneous bleeding, and throbbing. Constitutional symptoms were present but minimal. The extent of inflammation present at any given time following envenomation was found to be a more accurate diagnostic signal than the speed with which it developed. This case is similar to that of bites by juveniles of other species of viperines and crotalines and may serve to aid in the diagnosis and treatment of bites by juvenile specimens of serpents in these families.