Impact of defined clinical population and missing data on temporal trends in HIV viral load estimation within a health care system.

OBJECTIVES: Community viral load (CVL) estimates vary based on analytic methods. We extended the CVL concept and used data from the Veterans Health Administration (VA) to determine trends in the health care system viral load (HSVL) and its sensitivity to varying definitions of the clinical population and assumptions regarding missing data. METHODS: We included HIV-infected patients in the Veterans Aging Cohort Study, 2000-2010, with at least one documented CD4 count, HIV-1 RNA or antiretroviral prescription (n = 37 318). We created 6-month intervals including patients with at least one visit in the past 2 years. We assessed temporal trends in clinical population size, patient clinical status and mean HSVL and explored the impact of varying definitions of the clinical population and assumptions about missing viral load. RESULTS: The clinical population size varied by definition, increasing from 16 000-19 000 patients in 2000 to 23 000-26 000 in 2010. The proportion of patients with suppressed HIV-1 RNA increased over time. Over 20% of patients had no viral load measured in a given interval or the past 2 years. Among patients with a current HIV-1 RNA, mean HSVL decreased from 97 800 HIV-1 RNA copies/mL in 2000 to 2000 copies/mL in 2010. When current HIV-1 RNA data were unavailable and the HSVL was recalculated using the last available HIV-1 RNA, HSVL decreased from 322 300 to 9900 copies/mL. HSVL was underestimated when using only current data in each interval. CONCLUSIONS: The CVL concept can be applied to a health care system, providing a measure of health care quality. Like CVL, HSVL estimates depend on definitions of the clinical population and assumptions about missing data.

Towards a combined prognostic index for survival in HIV infection: the role of 'non-HIV' biomarkers.

BACKGROUND: As those with HIV infection live longer, 'non-AIDS' condition associated with immunodeficiency and chronic inflammation are more common. We ask whether 'non-HIV' biomarkers improve differentiation of mortality risk among individuals initiating combination antiretroviral therapy (cART). METHODS: Using Poisson models, we analysed data from the Veterans Aging Cohort Study (VACS) on HIV-infected veterans initiating cART between 1 January 1997 and 1 August 2002. Measurements included: HIV biomarkers (CD4 cell count, HIV RNA and AIDS-defining conditions); 'non-HIV' biomarkers (haemoglobin, transaminases, platelets, creatinine, and hepatitis B and C serology); substance abuse or dependence (alcohol or drug); and age. Outcome was all cause mortality. We tested the discrimination (C statistics) of each biomarker group alone and in combination in development and validation data sets, over a range of survival intervals, and adjusting for missing data. RESULTS: Of veterans initiating cART, 9784 (72%) had complete data. Of these, 2566 died. Subjects were middle-aged (median age 45 years), mainly male (98%) and predominantly black (51%). HIV and 'non-HIV' markers were associated with each other (P < 0.0001) and discriminated mortality (C statistics 0.68-0.73); when combined, discrimination improved (P < 0.0001). Discrimination for the VACS Index was greater for shorter survival intervals [30-day C statistic 0.86, 95% confidence interval (CI) 0.80-0.91], but good for intervals of up to 8 years (C statistic 0.73, 95% CI 0.72-0.74). Results were robust to adjustment for missing data. CONCLUSIONS: When added to HIV biomarkers, 'non-HIV' biomarkers improve differentiation of mortality. When evaluated over similar intervals, the VACS Index discriminates as well as other established indices. After further validation, the VACS Index may provide a useful, integrated risk assessment for management and research.

Estimating the impact of alcohol consumption on survival for HIV+ individuals.

Alcohol consumption is associated with decreased antiretroviral adherence, and decreased adherence results in poorer outcomes. However the magnitude of alcohol's impact on survival is unknown. Our objective was to use a calibrated and validated simulation of HIV disease to estimate the impact of alcohol on survival. We incorporated clinical data describing the temporal and dose-response relationships between alcohol consumption and adherence in a large observational cohort (N=2,702). Individuals were categorized as nondrinkers (no alcohol consumption), hazardous drinkers (consume > or =5 standard drinks on drinking days), and nonhazardous drinkers (consume <5 standard drinks on drinking days). Our results showed that nonhazardous alcohol consumption decreased survival by more than 1 year if the frequency of consumption was once per week or greater, and by 3.3 years (from 21.7 years to 18.4 years) with daily consumption. Hazardous alcohol consumption decreased overall survival by more than 3 years if frequency of consumption was once per week or greater, and by 6.4 years (From 16.1 years to 9.7 years) with daily consumption. Our results suggest that alcohol is an underappreciated yet modifiable risk factor for poor survival among individuals with HIV.

Explaining variability in the relationship between antiretroviral adherence and HIV mutation accumulation.

OBJECTIVES: Determining the relationship between antiretroviral adherence and resistance accumulation is important for the design and evaluation of adherence interventions. Our objective was to explain heterogeneity observed in this relationship. METHODS: We first conducted a systematic review to locate published reports describing the relationship between adherence and resistance. We then used a validated computer simulation to simulate the patient populations in these reports, exploring the impact of changes in individual patient characteristics (age, CD4, viral load, prior antiretroviral experience) on the shape of the adherence-resistance (A-R) curve. RESULTS: The search identified 493 titles, of which 3 contained relevant primary data and 2 had sufficient follow-up for inclusion (HOMER and REACH cohorts). When simulating HOMER, the A-R curve had a high peak with a greatly increased hazard ratio (HR) of accumulating mutations at partial compared to complete adherence (simulation, HR 2.9; HOMER, HR 2.7). When simulating REACH, the A-R curve had a shallow peak with a slightly increased hazard of accumulating mutations at partial adherence (simulation, HR 1.2; REACH, HR 1.4). This heterogeneity was primarily attributable to differences in antiretroviral experience between the cohorts. CONCLUSIONS: Our computer simulation was able to explain much of the heterogeneity in observed A-R curves.

Use of medical emergency team responses to reduce hospital cardiopulmonary arrests.

BACKGROUND: Medical emergency team (MET) responses have been implemented to reduce inpatient mortality, but data on their efficacy are sparse and there have been no reports to date from US hospitals. OBJECTIVES: To determine how the incidence and outcomes of cardiac arrests have changed following increased use of MET. METHODS: Objective criteria for MET activation were created and disseminated as part of a crisis management program, after which there was a rapid and sustained increase in the use of MET. A retrospective analysis of clinical outcomes was performed to compare the incidence and mortality of cardiopulmonary arrest before and after the increased use of MET. RESULTS: A retrospective analysis of 3269 MET responses and 1220 cardiopulmonary arrests over 6.8 years showed an increase in MET responses from 13.7 to 25.8 per 1000 admissions (p<0.0001) after instituting objective activation criteria. There was a coincident 17% decrease in the incidence of cardiopulmonary arrests from 6.5 to 5.4 per 1000 admissions (p = 0.016). The proportion of fatal arrests was similar before and after the increase in use of MET. CONCLUSIONS: Increased use of MET may be associated with fewer cardiopulmonary arrests.

Use of medical emergency team (MET) responses to detect medical errors.

BACKGROUND: No previous studies have investigated whether medical emergency team (MET) responses can be used to detect medical errors. OBJECTIVES: To determine whether review of MET responses can be used as a surveillance method for detecting medical errors. METHODS: Charts of all patients receiving MET responses during an 8 month period were reviewed by a hospital based Quality Improvement Committee to establish if the clinical deterioration that prompted the MET response was associated with a medical error (defined as an adverse event that was preventable with the current state of medical knowledge). Medical errors were categorized as diagnostic, treatment, or preventive errors using a descriptive typology based on previous published reports. RESULTS: Three hundred and sixty four consecutive MET responses underwent chart review and 114 (31.3%) were associated with medical errors: 77 (67.5%) were categorized as diagnostic errors, 68 (59.6%) as treatment errors, and 30 (26.3%) as prevention errors. Eighteen separate hospital care processes were identified and modified as a result of this review, 10 of which involved standardization. CONCLUSIONS: MET review may be used for surveillance to detect medical errors and to identify and modify processes of care that underlie those errors.

Matrix metalloproteases of the developing sea urchin embryo.

A distinct group of metalloproteases has been identified in the developing sea urchin embryo by gelatin substrate gel zymography, a highly sensitive protease detection assay. The developing Arbacia embryo exhibited four prominent bands of gelatinase activity with apparent molecular masses of 55, 50, 42 and 38 kDa. The activity of the 55, 42 and 38 kDa tissue gelatinases increased and that of the 50 kDa tissue gelatinase decreased during embryonic development. All four enzymes were EDTA- and 1,10-phenanthroline sensitive and phenyl methyl sulphonyl fluoride (PMSF) insensitive. None of the enzymes had detectable caseinolytic activity in casein substrate gels. Although the Arbacia enzymes possessed a number of properties that are characteristic of the mammalian matrix metalloprotease family, they did not appear to be converted to lower molecular weight forms by organomercurial treatment and are distinct in this aspect. The Arbacia metalloproteases are candidate enzymes for the tissue and matrix remodeling that occurs during sea urchin embryo development.

Role of calcium and calmodulin in the regulation of the rabbit ileal brush-border membrane Na+/H+ antiporter.

In rabbit ileum, Ca2+/calmodulin (CaM) appears to be involved in physiologically inhibiting the linked NaCl absorptive process, since inhibitors of Ca2+/CaM stimulate linked Na+ and Cl- absorption. The role of Ca2+/CaM-dependent phosphorylation in regulation of the brush-border Na+/H+ antiporter, which is believed to be part of the neutral linked NaCl absorptive process, was studied using purified brush-border membrane vesicles, which contain both the Na+/H+ antiporter and Ca2+/CaM-dependent protein kinase(s) and its phosphorprotein substrates. Rabbit ileal villus cell brush-border membrane vesicles were prepared by Mg precipitation and depleted of ATP. Using a freezethaw technique, the ATP-depleted vesicles were loaded with Ca2+, CaM, ATP and an ATP-regenerating system consisting of creatine kinase and creatine phosphate. The combination of Ca2+/CaM and ATP inhibited Na+/H+ exchange by 45 +/- 13%. This effect was specific since Ca2+/CaM and ATP did not alter diffusive Na+ uptake, Na+-dependent glucose entry, or Na+ or glucose equilibrium volumes. The inhibition of the Na+/H+ exchanger by Ca2+/CaM/ATP was due to an effect on the Vmax and not on the Km for Na+. In the presence of CaM and ATP, Ca2+ caused a concentration-dependent inhibition of Na+ uptake, with an effect 50% of maximum occurring at 120 nM. This Ca2+ concentration dependence was similar to the Ca2+ concentration dependence of Ca2+/CaM-dependent phosphorylation of specific proteins in the vesicles. The Ca2+/CaM/ATP-inhibition of Na+/H+ exchange was reversed by W13, a Ca2+/CaM antagonist, but not by a hydrophobic control, W12, or by H-7, a protein kinase C antagonist. We conclude that Ca2+, acting through CaM, regulates ileal brush-border Na+/H+ exchange, and that this may be involved in the regulation of neutral linked NaCl absorption.

Regulation of the rabbit ileal brush-border Na+/H+ exchanger by an ATP-requiring Ca++/calmodulin-mediated process.

Brush-border vesicles purified from rabbit ileal villus cells were used to evaluate how Ca++/calmodulin (CaM) regulates the neutral linked NaCl absorptive process, part of which is a Na+/H+ exchanger. After freezing and thawing to allow incorporation of macromolecules into the vesicles, the effect of Ca++/CaM on brush-border Na+ uptake with an acid inside pH gradient, and on Na+/H+ exchange was determined. Freezing and thawing vesicles with 0.85 microM free Ca++ plus 5 microM exogenous CaM failed to alter Na+/H+ exchange as did the addition of exogenous ATP plus an ATP regenerating system, which was sufficient to elevate intravesicular ATP to 47 microM from a basal level of 0.4 microM. However, the combination of Ca++/CaM plus ATP inhibited Na+ uptake in the presence of an acid inside pH gradient and inhibited Na+/H+ exchange, while Na+ uptake in the absence of a pH gradient was not altered. This effect required a hydrolyzable form of ATP, and did not occur when the nonhydrolyzable ATP analogue, AMP-PNP, replaced ATP. Under the identical intravesicular conditions used for the transport studies, Ca++ (0.85 microM) plus exogenous CaM (5 microM), in the presence of magnesium plus ATP, increased phosphorylation of five brush-border peptides. These data are consistent with Ca++/CaM acting via phosphorylation to regulate the ileal brush-border Na+/H+ exchanger.