A randomized controlled open trial of population-based disease and case management in a Medicare Plus Choice health maintenance organization

INTRODUCTION

The object of this study was to examine the effect of population-based disease management and case management on resource use, self-reported health status, and member satisfaction with and retention in a Medicare Plus Choice health maintenance organization (HMO).

METHODS

Study design consisted of a prospective, randomized controlled open trial of 18 months' duration. Participants were 8504 Medicare beneficiaries aged 65 and older who had been continuously enrolled for at least 12 months in a network model Medicare Plus Choice HMO serving a contiguous nine-county metropolitan area. Members were care managed with an expert clinical information system and frequent telephone contact. Main outcomes included self-reported health status measured by the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), resource use measured by admission rates and bed-days per thousand per year, member satisfaction, and costs measured by paid claims.

RESULTS

More favorable outcomes occurred in the intervention group for satisfaction with the health plan (P < .01) and the social function domain as measured by SF-36 (P = .04). There was no difference in member retention or mortality between groups. Use of skilled nursing home services was significantly lower in the intervention group than in the control (616 vs 747 days per thousand members per year, P = .02). This reduction, however, did not lead to lower mean total expenditures in the intervention group compared with the control (6828 dollars per member for 18 months vs 7001 dollars, P = .61).

CONCLUSION

Population-based disease management and case management led to improved self-reported satisfaction and social function but not to a global net decrease in resource use or improved member retention.

What care should be covered?

The answer to the question of what health care services should be covered by a managed care plan is straightforward; the plan should cover whatever the consumer is willing to pay for. From the plan's perspective, the consumer is the payer, that is, the employer who negotiates the plan; not the individual patient whose personal preferences and interests may be quite different. Since managed care organizations contract with payers to arrange for health care services within a defined set of benefits, there is a broader question as well: Within the benefits chosen by the payer, what actually is covered? Criteria for determining "medical necessity," which managed care plans frequently use as the basis for coverage, are discussed.

Strongyloides infection and meningitis in an immunocompromised host

Strongyloidiasis and aseptic meningitis occurred in a renal transplant recipient who was receiving immunosuppressive drugs. Cure followed therapy with antibiotic administration for 3 days combined with oral thiabendazole, suggesting parasitic infection as the most likely cause of meningitis. Awareness of this disease and need for prompt institution of therapy is stressed. Prophylactic administration of thiabendazole is probably preventive.

Comparative efficacy of piperacillin and penicillin G in treatment of gonococcal urethritis

The comparative efficacy of 2 g of piperacillin and 4.8 X 10(6) U of penicillin G in the treatment of uncomplicated gonococcal urethritis was assessed in a randomized prospective study. Sixty-five evaluable patients received piperacillin, and 55 received penicillin G. All patients received either therapy were cured of gonorrhea. We conclude that piperacillin is as efficacious as aqueous procaine penicillin G in the therapy of uncomplicated gonococcal urethritis.

Role of surface fimbriae (fibrils) in the adsorption of Actinomyces species to saliva-treated hydroxyapatite surfaces

We studied the adsorption, morphological, and serological characteristics of selected Actinomyces and related species. Evaluation of uranyl acetate-stained cells by electron microscopy revealed wide variations among strains in the frequency of surface fimbriae. These variations did not always correlate with the percent adsorption to saliva-treated hydroxyapatite of the various Actinomyces strains. However, two strains of Rothia dentocariosa possessing no surface fimbriae and five strains of A. israelii possessing very few surface fimbriae exhibited feeble adsorption to saliva-treated hydroxyapatite. Although the calculated number of adsorption sites on saliva-treated hydroxypatite did not vary widely among the strains tested, significant differences were observed in the affinities calculated for some species or serotypes. The mean affinities for strains of A. viscosus serotype 2 and A. naeslundii serotype 3 were similar, and these strains adsorbed well to saliva-treated hydroxyapatite. The mean adsorption and affinity for the A. naeslundii strain serotype 1 and all strains of A. israelii tested were significantly less than those determined for the A. viscosus serotype 2 or A. naeslundii serotype 3 strains. Adsorption inhibition activity of antiserum to strain T14V, previously shown to be solely related to antibodies in immune serum directed against the VA1 fimbria (fibril) antigen, was removed by preadsorption of the antiserum with most A. viscosus and A. naelundii strains, but not with A. israelii strains. This suggests some cross-reactivity among strains of A. viscosus and A. naeslundii but not A. israelii. Adsorption to saliva-treated hydroxyapatite of all A. viscosus and A. naeslundii strains tested was strongly inhibited by fimbriae isolated from A. viscosus strain T14V. Collectively, these data suggest that the adsorption of certain A. viscosus and A. naeslundii strains is mediated by surface fimbriae, many of which appear serologically cross-reactive with strain T14V fimbriae.

Non-immunological precipitation by the neutral detergent triton X-100 in agar gel diffusion

Triton X-100 can be used to clarify vague immunoprecipitin lines from bacterial antigens; however, non-immunological precipitation can lead to mistaken interpretation of immunodiffusion results. If Triton X-100 is added directly to the gel during preparation rather than to the antigen well, this detergent artifact can be eliminated.

Gonococcal endocarditis

Two cases of gonococcal endocarditis and their clinical features have been described. This uncommon disease typically presents in a subacute fashion but may progress to a rapidly destructive, lethal process within days. We therefore recommend a conservative approach to therapy for disseminated gonococcal infection.

Immunochemical differences between oral and nonoral strains of Bacteroides asaccharolyticus

We undertook a morphological and immunochemical comparison of purified outer membrane antigens from oral and nonoral isolates of Bacteroides asaccharolyticus. Electron micrographs of thin sections of whole bacteria revealed a compact, electron-dense capsule external to the outer membrane of oral strains. A loose, web-like material was noted on the surface of several nonoral strains that was distinct from the dense capsule seen on oral strains. Polyacrylamide gel electrophoresis showed distinct differences in the protein band pattern between oral and nonoral isolates; sugar composition was similar with a few exceptions. An indirect fluorescent-antibody test utilizing antiserum to a purified capsular antigen from a single oral strain cross-reacted with all of numerous oral and nonoral strains of B. asaccharolyticus, thereby demonstrating a shared antigen that is species specific for B. asaccharolyticus. However, antibodies to an oral strain-derived capsular antigen were detectable by enzyme immunoassay only in serum from rabbits immunized with oral strains. Thus, definite morphological and immunochemical differences were found between oral and nonoral isolates of B.asaccharolyticus.

Detection of anticapsular antibodies to Bacteroides asaccharolyticus in serum from rabbits and humans by use of an enzyme-linked immunosorbent assay

A sensitive serologic test, the enzyme-linked immunosorbent assay (ELISA), was used to detect serum IgG antibodies directed specifically to a capsular antigen of Bacteroides asaccharolyticus (previously known as Bacteroides melaninogenicus subspecies asaccharolyticus). Anticapsular IgG was measured in 30 specimens of rabbit serum after the animals were immunized with whole B. asaccharolyticus, the two subspecies of B. melaninogenicus, and several other bacterial species. Species-specific anticapsular IgG was demonstrated (P less than 0.001). Levels of anticapsular IgG greater than control levels were likewise detected in serum from two humans, including one patient who had periodontitis and from whom B. asaccharolyticus was isolated, and a laboratory worker who had extensive exposure over a two-year period to B. asaccharolyticus. The ELISA was found to be a relatively simple, sensitive tool for measurement of serum IgG. Its application to detection of immunoglobulins of other classes, including secretory IgA, is anticipated, provided adequate standardization methods are used.

The cell envelope of the Legionnaires' disease bacterium. Morphologic and biochemical characteristics

We studied the cell-envelope structure of the Legionnaires' disease (LD) bacterium by electron microscopy and biochemical assays. There were apparent differences in cell structure by electron microscopy using two different prefixation methods. Organisms prefixed with gluteraldehyde had a single surrounding membrane. The typical two-membrane structure of gram-negative bacteria, however, was observed after prefixation with a combination of gluteraldehyde, formalin, and creosol. The cell wall (peptidoglycan) was seen in electron micrographs of plasmolyzed bacteria and in papain-digested cells. Both cytoplasmic and outer membranes were separated by differential centrifugation of spheroplast sonicates followed by sucrose density gradient ultracentrifugation. We identified each membrane by characteristic enzyme activity (cytoplasmic membrane) and 2-keto-3-deoxyoctonate content (outer membrane).

Experimental animal models for anaerobic infections

An experimental animal model that stimulates the mixed aerobic-anaerobic microflora of intraabdominal sepsis was used to study antimicrobial efficacy in vivo. Treatment of infected rats with chloramphenicol resulted in only a modest reduction in the percentage of animals surviving infection with abscesses at necropsy. This unanticipated observation led to further exploration of the predominant anaerobes associated with the experimental infection. In vitro cultures of Bacteroides fragilis, susceptible to chloramphenicol in traditional tests, were capable of reducing chloramphenicol to its aryl amine derivative, which is biologically inactive. In contrast, metronidazole, an antimicrobial agent active against anaerobes, reduced the coli-metronidazole, an antimicrobial agent active against anaerobes, reduced the coli-form-associated mortality in this animal model. Subsequent studies showed that this reduction in mortality is dependent on the presence of an anaerobe and that the levels of Escherichia coli in mixed continuous culture with B. fragilis are reduced by addition of metronidazole. This reduction following addition of metronidazole was not observed either in a pure culture of E. coli or when clindamycin was added to a mixed culture. In a modification of the previously described model, infective material was placed subcutaneously into Wistar rats. Studies with this model suggested that the host's response to bacterial challenge is dependent on the site of infection and that organotropism of the implanted bacterial species is an important determinant of infection.

Immunochemical characterization of surface antigens of Bacteroides melaninogenicus

Major surface antigens of Bactmbrane complex by gentle methods, purified, and characterized immunochemically. A lipopolysaccharide (LPS) was found to be chemically distinct from the LPS of facultative gram-negative bacteria in that it lacked two core sugars, 2-keto-3-deoxyoctonate and heptose, as well as beta-hydroxymyristic acid, the predominant fatty acid in the lipid A moiety. The LPS was further atypical in that it had a very low level of biologic activity. A capsular polysaccharide was demonstrated morphologically by electron microscopy with ruthenium red staining and a ferritin-labeled antibody technique. This antigen was shown to be subspecies-specific by indirect immunofluorescence. Antibody to the capsular polysaccharide was measured by an enzyme-linked immunospecific assay. The presence of a relatively impotent LPS and a surface capsular antigen may partly explain the rarity of bacteremia and septic shock due to B. melaninogenicus subspecies asaccharolyticus and the common association of this organism with abscess formation.

Identification of a subspecies-specific capsular antigen from Bacteroides melaninogenicus subspecies asaccharolyticus by immunofluorescence and electron microscopy

An indirect fluorescent antibody test was developed with the use of hyperimmune rabbit antiserum to a purified capsular polysaccharide of Bacteroides melaninogenicus subspecies asaccharolyticus. All of 23 strains of B. melaninogenicus subspecies asaccharolyticus were fluorescence-positive in this test. All 11 strains of Bacteroides melaninogenicus subspecies intermedius tested and three strains of Bacteroides melaninogenicus subspecies melaninogenicus were fluorescence-negative. Thirty-one strains of other bacterial species were also fluorescence-negative. The indirect fluorescent antibody test demonstrated the presence of a subspecies-specific capsular antigen from B. melaninogenicus subspecies asaccharolyticus. The capsular antigen was further demonstrated by electron microscopy with ruthenium red, a polysaccharide-staining material.

Immunochemical and Biologic Studies of the Lipopolysaccharide of Bacteroides Melaninogenicus Subspecies Asaccharolyticus

Lipopolysaccharide (LPS) was isolated from the outer membrane complex of Bacteroides melaninogenicus by gel chromatography by using sodium deoxycholate (NaD), an endotoxin-disaggregating detergent in the running buffer. Reaggregation occurred after removal of residual NaD. LPS was also prepared by the phenol/water method for comparison. The LPS was composed of loosely bound lipid (62%) and carbohydrate (32%), with less than 5% protein. Glucose, galactose, and glucosamine were the major sugars as detected by gas-liquid chromatography (GLC). Heptose and 2-keto-3-deoxyoctonate (KDO) were found to be absent when using colorimetric tests. Fatty acid analysis by GLC disclosed an unusual pattern; β-OH myristic acid was notably absent. Biologic activity was assessed with the dermal Shwartzman test, the Limulus lysate assay, and the chick embryo lethality test. LPS preparations gave no positive skin reactions in rabbits in doses up to 1 mg, compared to Salmonella typhi 0:901 endotoxin which was positive at 12.5 µg. Limulus lysate gelation and chick embryo lethality occurred at doses 30-fold or more different from Salmonella endotoxin controls. Hemagglutination inhibition (HAI) studies demonstrated the presence of capsular polysaccharide as a contaminant found in the phenol/water extracted LPS. This polysaccharide could be removed partially by further purifying the LPS with ultracentrifugation.

The LPS of B. melaninogenicus lacks two of the core sugars characteristic of aerobic Gram-negative endotoxins, has a unique fatty acid composition, and displays low biologic potency. These findings may explain the rarity of septic shock in patients infected with this organism. The presence of capsular polysaccharide contaminating the phenol/water-extracted LPS may explain partially the serologic heterogeneity which has been described previously in studies of the LPS of this organism.

Purification and immunochemical characterization of the outer membrane complex of Bacteroides melaninogenicus subspecies asaccharolyticus

Morphologic study of Bacteroides melaninogenicus subspecies asaccharolyticus by electron microscopy disclosed the presence of a capsule and a cell wall structure otherwise typical of a gram-negative organism. An outer membrane complex was isolated with use of gentle methods. Relative purity of the preparation was confirmed by electron microscopy and by the formation of a single band in a sucrose density gradient. Gel chromatography was used for separation of the major components of the membrane. Antigenicity of the first component, a protein-polysaccharide complex, which cross-reacted with antiserum to another strain of the same subspecies. This component probably represents the capsular antigen and may prove to be the basis for serogrouping. The second membrane fraction differed chemically from the first fraction and represents the lipopolysaccharide component of the outer membrane. Notably, this component lacks 2-keto-3-deoxyoctonate, one of the backbone sugars of aerobic, gram-negative lipopolysaccharides.