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PubMed2005

Factors explaining the intention to give blood among the general population.

BACKGROUND AND OBJECTIVES: The aim of this study was to identify factors explaining the intention to donate blood. MATERIALS AND METHODS: A random sample of 4000 respondents drawn from the general population received a questionnaire by mail. This questionnaire assessed variables as defined by the most prominent social cognitive theories. RESULTS: Overall, the respondents expressed a neutral mean level of intention to give blood in the next 6 months (2.84 on a five-point scale); 56.2% had never given blood in the past. The variables explaining 74% of the variance of intention were: perceived behavioural control (beta = 0.39; P < 0.001); factors facilitating taking action (beta = 0.25; P < 0.001); anticipated regret (beta = 0.16; P < 0.001); moral norm (beta = 0.11; P < 0.001); attitude (beta = 0.08; P < 0.01); level of education (beta = -0.03; P < 0.05); and past experience in giving blood (beta = 0.09; P < 0.001). Nonetheless, the predictive power of perceived behavioural control and moral norm was higher among the ever donors (both at P < 0.01) compared to the never donors, whereas the reverse was observed for attitude (P < 0.05). CONCLUSIONS: People's intentions are mainly determined by perceived barriers and obstacles regarding blood donations. This suggests that promotional strategies should focus on the elimination of barriers to action as well as the development of a higher perception of control. Also, messages should be adapted to the targeted population, based on their previous blood donation behaviour (i.e. never donors vs. ever donors).

Adolescent↗

PubMed2000

Weak common parallel fibre synapses explain the loose synchrony observed between rat cerebellar golgi cells.

1. In anaesthetized rats, pairs of cerebellar Golgi cells fired synchronously at rest, provided they were aligned along the parallel fibre axis. The observed synchrony was much less precise, however, than that which would be expected to result from common, monosynaptic parallel fibre excitation. 2. To explain this discrepancy, the precision and frequency of spike synchronization (i.e. the width and area of the central peak on the spike train cross-correlogram) were computed in a generic model for varying input, synaptic and neuronal parameters. 3. Correlation peaks between model neurons became broader, and peak area smaller, when the number of afferents increased and each single synapse decreased proportionally in strength. Peak width was inversely proportional to firing rate, but independent of the percentage of shared afferents. Peak area, in contrast, scaled with the percentage of shared afferents but was almost firing rate independent. 4. Broad correlation peaks between pairs of model neurons resulted from the loose spike timing between single model neurons and their afferents. This loose timing reflected a need for long-term synaptic integration to fire the neurons. Model neurons could accomplish this through firing rate adaptation mediated by a Ca2+-activated K+ channel. 5. We conclude that loose synchrony may be entirely explained by shared input from monosynaptic, non-synchronized afferents. The inverse relationship between peak width and firing rate allowed us to distinguish common parallel fibre input from firing rate covariance as a primary cause of loose synchrony between cerebellar Golgi cells in anaesthetized rats.

Action Potentials↗

PubMed2001

Can obstetric complications explain the high levels of obstetric interventions and maternity service use among older women? A retrospective analysis of routinely collected data.

OBJECTIVE: To determine whether the higher levels of obstetric intervention and maternity service use among older women can be explained by obstetric complications. DESIGN: A retrospective analysis of routinely collected data from the Aberdeen Maternity and Neonatal Databank. PARTICIPANTS: All residents of Aberdeen city district delivering singleton infants at the Maternity Hospital 1988-1997 (28,484 deliveries). MAIN OUTCOME MEASURES: Odds ratios for each intervention in older maternal age groups compared with women aged 20-29. Interventions considered include obstetric interventions (induction of labour, augmentation, epidural use, assisted delivery, caesarean section) and raised maternity service use (more than two prenatal scans, amniocentesis, antenatal admission to hospital, admission at delivery of more than five days, infant resuscitation, and admission to the neonatal unit). METHODS: Logistic regression was used to investigate the association between maternal age and the incidence of interventions. The odds ratios for each intervention were then adjusted for relevant obstetric complications and maternal socio-demographic characteristics. RESULTS: Levels of amniocentesis, caesarean section, assisted delivery, induction, and augmentation (in primiparae) are all higher among older women. Maternity service use also increases significantly with age: older women are more likely to have an antenatal admission, more than two scans, a hospital stay at delivery of more than five days, and have their baby admitted to a neonatal unit. Controlling for relevant obstetric complications reveals several examples of effect modification, but does not eliminate the age effect for most interventions in most groups of women. CONCLUSIONS: Higher levels of intervention among older women are not explained by the obstetric complications we considered.

Adult↗

PubMed2005

How much variation in CS rates can be explained by case mix differences?

OBJECTIVE: To quantify the amount of variation in caesarean section (CS) rates between maternity units explained by case mix differences. DESIGN: Cross-sectional study. SETTING: All 216 maternity units in England and Wales. POPULATION: Women giving birth at these maternity units between May and July 2000. METHODS: Logistic regression models were developed to investigate the relationship between case mix characteristics, and odds of (i) CS before labour, (ii) CS in labour. Using these results, overall CS rates standardised for case mix were calculated for each maternity unit. Random-effects meta-analysis was used to examine heterogeneity between maternity units. MAIN OUTCOME MEASURES: CS before labour and CS during labour. RESULTS: Adjustment for case mix differences between maternity units explained 34% of the variance in CS rates. Odds of CS (before and in labour) increased with maternal age. Women from ethnic minority groups had lower odds of CS before labour, and increased odds of CS in labour. Women with a previous vaginal delivery had lower odds of CS, although the magnitude of this for CS before and in labour is markedly different. CONCLUSIONS: Case mix adjustment is important to enable understanding of the factors that influence the CS rate. These include organisational and staffing levels as well as women's preferences for childbirth and clinician's attitudes. An understanding of how these factors influence the CS rate is essential for evaluation of quality and appropriateness of obstetric care provided to women.

Adolescent↗

PubMed2004

Context or composition: what explains variation in SCHIP disenrollment?

OBJECTIVE: To investigate (1) the relative contributions of family and contextual characteristics to observed variation in disenrollment rates from the State Children's Health Insurance Program (SCHIP), and (2) whether context explains observed family-level patterns. DATA SOURCES: We use secondary data on 24,628 families enrolled in New Jersey's SCHIP program (NJ KidCare), and county-level data from the Area Resource File, the Census, and the NJ FamilyCare provider roster. STUDY DESIGN: Information on family characteristics, SCHIP plan, and dates of enrollment and disenrollment are taken from NJ KidCare administrative records, which provided surveillance data from January 1998 through April 2000. DATA COLLECTION/ANALYSIS: We estimate a multilevel discrete-time-hazards model of SCHIP disenrollment. FINDINGS: Families enrolled in plans involving cost-sharing, blacks, and those with only one enrolled child have higher than average rates of disenrollment. Disenrollment rates for blacks are lower in counties with a high share of black physicians. These characteristics account for part of the intercounty variation in disenrollment rates; remaining intercounty variation is largely explained by physician density or population density. POLICY IMPLICATIONS: It may be worthwhile to pay special attention to black families and counties with high disenrollment rates to address the reasons for their lower retention. Addressing cultural differences between physician and client and the geographic distribution of medical providers might reduce disenrollment.

Child↗

PubMed2006

Can differences in breast cancer utilities explain disparities in breast cancer care?

BACKGROUND: Black, older, and less affluent women are less likely to receive adjuvant breast cancer therapy than their counterparts. Whereas preference contributes to disparities in other health care scenarios, it is unclear if preference explains differential rates of breast cancer care. OBJECTIVE: To ascertain utilities from women of diverse backgrounds for the different stages of, and treatments for, breast cancer and to determine whether a treatment decision modeled from utilities is associated with socio-demographic characteristics. PARTICIPANTS: A stratified sample (by age and race) of 156 English-speaking women over 25 years old not currently undergoing breast cancer treatment. DESIGN AND MEASUREMENTS: We assessed utilities using standard gamble for 5 breast cancer stages, and time-tradeoff for 3 therapeutic modalities. We incorporated each subject's utilities into a Markov model to determine whether her quality-adjusted life expectancy would be maximized with chemotherapy for a hypothetical, current diagnosis of stage II breast cancer. We used logistic regression to determine whether socio-demographic variables were associated with this optimal strategy. RESULTS: Median utilities for the 8 health states were: stage I disease, 0.91 (interquartile range 0.50 to 1.00); stage II, 0.75 (0.26 to 0.99); stage III, 0.51 (0.25 to 0.94); stage IV (estrogen receptor positive), 0.36 (0 to 0.75); stage IV (estrogen receptor negative), 0.40 (0 to 0.79); chemotherapy 0.50 (0 to 0.92); hormonal therapy 0.58 (0 to 1); and radiation therapy 0.83 (0.10 to 1). Utilities for early stage disease and treatment modalities, but not metastatic disease, varied with socio-demographic characteristics. One hundred and twenty-two of 156 subjects had utilities that maximized quality-adjusted life expectancy given stage II breast cancer with chemotherapy. Age over 50, black race, and low household income were associated with at least 5-fold lower odds of maximizing quality-adjusted life expectancy with chemotherapy, whereas women who were married or had a significant other were 4-fold more likely to maximize quality-adjusted life expectancy with chemotherapy. CONCLUSIONS: Differences in utility for breast cancer health states may partially explain the lower rate of adjuvant therapy for black, older, and less affluent women. Further work must clarify whether these differences result from health preference alone or reflect women's perceptions of sources of disparity, such as access to care, poor communication with providers, limitations in health knowledge or in obtaining social and workplace support during therapy.

Adult↗

PubMed2005

Counterfactual links to the proportion of treatment effect explained by a surrogate marker.

In a randomized clinical trial, a statistic that measures the proportion of treatment effect on the primary clinical outcome that is explained by the treatment effect on a surrogate outcome is a useful concept. We investigate whether a statistic proposed to estimate this proportion can be given a causal interpretation as defined by models of counterfactual variables. For the situation of binary surrogate and outcome variables, two counterfactual models are considered, both of which include the concept of the proportion of the treatment effect, which acts through the surrogate. In general, the statistic does not equal either of the two proportions from the counterfactual models, and can be substantially different. Conditions are given for which the statistic does equal the counterfactual model proportions. A randomized clinical trial with potential surrogate endpoints is undertaken in a scientific context; this context will naturally place constraints on the parameters of the counterfactual model. We conducted a simulation experiment to investigate what impact these constraints had on the relationship between the proportion explained (PE) statistic and the counterfactual model proportions. We found that observable constraints had very little impact on the agreement between the statistic and the counterfactual model proportions, whereas unobservable constraints could lead to more agreement.

Anti-HIV Agents↗

PubMedDate not supplied

Factors explaining lack of response to heel stick in preterm newborns.

OBJECTIVE: To determine factors explaining lack of response by preterm newborns to heel stick for blood sampling. DESIGN: A cross-sectional design based on secondary analysis of the control session of a randomized crossover design. SETTING: Four Level III neonatal intensive-care units of university teaching hospitals. PARTICIPANTS: 120 preterm newborns with an average age of 28 weeks postconceptional age. INTERVENTION: 24 newborns who showed a "no change" response according the Premature Infant Pain Profile were compared to the remaining 96 newborns who had shown a pain response. MAIN OUTCOME MEASURES: Age (postconceptional age at birth, postnatal age at study), Apgar score at 5 minutes, severity of illness, sex, race, wake/sleep state, previous study sessions, total number of painful procedures since birth, and time since last painful procedure. RESULTS: After stepwise logistic regression analysis the variables remaining in the final model that explained the difference between the groups were postnatal age at time of study, postconceptional age at birth, time since last painful procedure, and wake/sleep state. CONCLUSIONS: Newborns who were younger, asleep, and had undergone a painful event more recently were less likely to demonstrate behavioral and physiologic indicators of pain.

Age Factors↗

PubMed2005

Carbapenem resistance mechanisms in Pseudomonas aeruginosa: alterations of porin OprD and efflux proteins do not fully explain resistance patterns observed in clinical isolates.

Imipenem resistance in Pseudomonas aeruginosa is considered to be associated with loss of the porin OprD combined with activity of chromosomal beta-lactamase (AmpC), while overexpression of multidrug efflux pumps is considered to confer meropenem resistance. Carbapenem resistance can also result from production of metallo-beta-lactamases. Transcription of oprD and efflux pump genes mexB, mexY and mexF was analysed in 23 clinical isolates of P. aeruginosa by quantitative RT-PCR. oprD was sequenced in all, and mexR, regulator of efflux pump MexAB-OprM, in selected isolates. Four isolates that were imipenem susceptible had significant reduction of oprD mRNA and presence of oprD mutations causing frameshift or translational stop. In strains only resistant to imipenem no significant difference in transcription of oprD was observed between low-level and high-level resistant isolates. The differences could not be explained by either pattern of oprD mutations. Increased transcription of mexB generally correlated well with meropenem resistance. One high-level meropenem-resistant isolate showed no significant change in mexB mRNA, but sequencing confirmed presence of a nalB mutation. Furthermore, one meropenem-susceptible isolate showed significant increase in mexB transcription, but no mexR mutations. In summary, our findings indicate that the resistance patterns observed cannot be fully explained by the currently described carbapenem resistance mechanisms.

Amino Acid Sequence↗

PubMed2000

The scientific origin of life. Considerations on the evolution of information, leading to an alternative proposal for explaining the origin of the cell, a semantically closed system.

We hypothesize that the origin of life, that is, the origin of the first cell, cannot be explained by natural selection among self-replicating molecules, as is done by the RNA-world hypothesis. To circumvent the chicken and egg problem associated with semantic closure of the cell--no replication of information molecules (nucleotide strands) without functional enzymes, no functional enzymes without encoding in information molecules--a prebiotic evolutionary process is proposed that, from the informational point of view, must somehow have resembled the current scientific process. The cell was the outcome of interactions of a complex premetabolic community, with information molecules that were devoid of self-replicative properties. In a comparable manner, scientific progress is possible, essentially because of interaction between a complex cultural society and permanent information carriers like printed matter. This may eventually lead to self-replicating technology in which semantic closure occurs anew. Explaining the origin of life as a scientific process might provide a unifying theory for the evolution of information, wherebye at two moments symbolization/encoding of interactions into permanent information occurred: at one moment that of chemical interaction and at another moment that of animal behavior interaction. In one event this encoding led to autonomously duplicating chemistry (the cell), an event that possibly may be one of the outcomes of current scientific progress.

Origin of Life↗

PubMed1993

Degree of breast emptying explains changes in the fat content, but not fatty acid composition, of human milk.

We compared within and between breastfeed changes in milk fat to short-term rates of milk synthesis and degree of breast emptying (measured using the Computerized Breast Measurement system) over two 24 h periods for five lactating mothers. The fat content (f) of fore and hind milk samples increased more steeply as the breast was progressively emptied by the infant (degree of emptying, d, range 0-1; f = 21.59 + 9.38d + 70.99d2; P < 0.0001; r2 = 0.68; n = 154). For the nine individual breasts, between 41-95% of the variance of the fat content of milk was explained by degree of breast emptying. We argue that this relationship explains differences in the circadian rhythm of the fat content of milk and allows the accurate calculation of the average fat content of milk consumed by infants (37-66 g/l for the nine individual breasts). The fatty acid composition of the fore and hind milk samples was determined for four of the mothers. We observed within and between breastfeed variability in the relative proportions of the seven major fatty acids of milk fat and these changes are discussed with reference to the control of fat synthesis in the human mammary gland.

Breast↗

PubMed2003

A reappraisal of the blood glucose homeostat which comprehensively explains the type 2 diabetes mellitus-syndrome X complex.

Blood glucose concentrations are unaffected by exercise despite very high rates of glucose flux. The plasma ionised calcium levels are even more tightly controlled after meals and during lactation. This implies 'integral control'. However, pairs of integral counterregulatory controllers (e.g. insulin and glucagon, or calcitonin and parathyroid hormone) cannot operate on the same controlled variable, unless there is some form of mutual inhibition. Flip-flop functional coupling between pancreatic alpha- and beta-cells via gap junctions may provide such a mechanism. Secretion of a common inhibitory chromogranin by the parathyroids and the thyroidal C-cells provides another. Here we describe how the insulin:glucagon flip-flop controller can be complemented by growth hormone, despite both being integral controllers. Homeostatic conflict is prevented by somatostatin-28 secretion from both the hypothalamus and the pancreatic islets. Our synthesis of the information pertaining to the glucose homeostat that has accumulated in the literature predicts that disruption of the flip-flop mechanism by the accumulation of amyloid in the pancreatic islets in type 2 diabetes mellitus will lead to hyperglucagonaemia, hyperinsulinaemia, insulin resistance, glucose intolerance and impaired insulin responsiveness to elevated blood glucose levels. It explains syndrome X (or metabolic syndrome) as incipient type 2 diabetes in which the glucose control system, while impaired, can still maintain blood glucose at the desired level. It also explains why it is characterised by high plasma insulin levels and low plasma growth hormone levels, despite normoglycaemia, and how this leads to central obesity, dyslipidaemia and cardiovascular disease in both syndrome X and type 2 diabetes.

Animals↗

PubMed2001

Two functionally distinct forms of a retroviral receptor explain the nonreciprocal receptor interference among subgroups B, D, and E avian leukosis viruses.

Subgroups B, D, and E avian leukosis viruses (ALV-B, -D, and -E) share the same chicken receptor, TVB(S1), a tumor necrosis factor receptor (TNFR)-related protein. These viruses, however, exhibit nonreciprocal receptor interference (NRI): cells preinfected with ALV-B or ALV-D are resistant to superinfection by viruses of all three subgroups, whereas those pre-infected by ALV-E are resistant only to superinfection by other subgroup E viruses. In this study, we investigated the basis of this phenomenon by characterizing the interaction of TVB(S1) with ALV-B Env or ALV-E Env. Sequential immunoprecipitation analysis using surface envelope immunoglobulin fusion proteins revealed the existence of two separate types of TVB(S1) that are encoded by the same cDNA clone. One form, designated the type 1 receptor, is specific for ALV-B and ALV-E. The other form, the type 2 receptor, is specific for ALV-B. We show that a protein consisting of only the first and second extracellular cysteine-rich domains of TVB(S1) is capable of forming both receptor types. However, the third extracellular cysteine-rich domain is required for efficient formation of the type 1 receptor. We also demonstrate that heterogeneous N-linked glycosylation cannot explain the difference in activities of the two receptor types. The existence of two types of TVB(S1) explains the NRI pattern between ALV-B and -E: subgroup B viruses establish receptor interference with both receptor types, whereas subgroup E viruses interfere only with the type 1 receptor, leaving the type 2 receptor available to mediate subsequent rounds of ALV-B entry. The formation of a TVB receptor type that is specific for cytopathic ALV may also have important implications for understanding how some subgroups of ALV cause cell death.

Amino Acid Sequence↗

PubMed1991

Explaining outputs of primary health care: population and practice factors.

OBJECTIVE: To examine whether variations in the activities of general practice among family health service authorities can be explained by the populations characteristics and the organisation and resourcing of general practice. DESIGN: The family health services authorities were treated as discrete primary health care systems. Nineteen performance indicators reflecting the size, distribution, and characteristics of the population served; the organisation of general practice (inputs); and the activities generated by general practitioners and their staff (output) were analysed by stepwise regression. SETTING: 90 family health services authorities in England. MAIN OUTCOME MEASURES: Rates of cervical smear testing, immunisation, prescribing, and night visiting. RESULTS: 53% of the variation in uptake of cervical cytology was accounted for by Jarman score (t = -3.3), list inflation (-0.41), the proportion of practitioners over 65 (-0.64), the number of ancillary staff per practitioner (2.5), and 70% of the variation in immunisation rates by standardised mortality ratios (-6.6), the proportion of practitioners aged over 65 (-4.8), and the number of practice nurses per practitioner (3.5). Standardised mortality ratios (8.4), the number of practitioners (2.3), and the proportion over 65 (2.2), and the number of ancillary staff per practitioner (-3.1) accounted for 69% of variation in prescribing rates. 54% of the variation in night visiting was explained by standardised mortality ratios (7.1), the proportion of practitioners with lists sizes below 1000 (-2.2), the proportion aged over 65 (-0.4), and the number of practice nurses per practitioner (-2.5). CONCLUSIONS: Family health services authorities are appropriate systems for studying output of general practice. Their performance indicators need to be refined and to be linked to other relevant factors, notably the performance of hospital, community, and social services.

England↗

PubMed1993

Explaining socioeconomic differences in sickness absence: the Whitehall II Study.

OBJECTIVE: To describe and explain the socioeconomic gradient in sickness absence. DESIGN: Analysis of questionnaire and sickness absence data collected from the first phase of the Whitehall II study. Grade of employment was used as a measure of socioeconomic status. SETTING: 20 civil service departments in London. SUBJECTS: 6900 male and 3414 female civil servants aged 35-55 years. MAIN OUTCOME MEASURES: Rates of short spells (< or = 7 days) and long spells (> 7 days) of sickness absence. RESULTS: A strong inverse relation between grade of employment and sickness absence was evident. Men in the lowest grade had rates of short and long spells of absence 6.1 (95% confidence interval 5.3 to 6.9) and 6.1 (4.8 to 7.9) times higher than those in the highest grade. For women the corresponding rate ratios were 3.0 (2.3 to 3.9) and 4.2 (2.5 to 6.8) respectively. Several risk factors were identified, including health related behaviours (smoking and frequent alcohol consumption), work characteristics (low levels of control, variety and use of skills, work pace, and support at work), low levels of job satisfaction, and adverse social circumstances outside work (financial difficulties and negative support). These risk factors accounted for about one third of the grade differences in sickness absence. CONCLUSION: Large grade differences in sickness absence parallel socioeconomic differences in morbidity and mortality found in other studies. Identified risk factors accounted for a small proportion of the grade differences in sickness absence. More accurate measurement of the risk factors may explain some of the remaining differences in sickness absence but other factors, as yet unrecognised, are likely to be important.

Absenteeism↗

PubMed1994

Changes in risk factors explain changes in mortality from ischaemic heart disease in Finland.

OBJECTIVES: To estimate the extent to which changes in the main coronary risk factors (serum cholesterol concentration, blood pressure, and smoking) explain the decline in mortality from ischaemic heart disease and to evaluate the relative importance of change in each of these risk factors. DESIGN: Predicted changes in ischaemic heart disease mortality were calculated by a logistic regression model using the risk factor levels assessed by cross sectional population surveys, in 1972, 1977, 1982, 1987, and 1992. These predicted changes were compared with observed changes in mortality statistics. SETTING: North Karelia and Kuopio provinces, Finland. SUBJECTS: 14,257 men and 14,786 women aged 30-59 randomly selected from the national population register. MAIN OUTCOME MEASURES: Levels of the risk factors and predicted and observed changes in mortality from ischaemic heart disease. RESULTS: The observed changes in the risk factors in the population from 1972 to 1992 predicted a decline in mortality from ischaemic heart disease of 44% (95% confidence interval 37% to 50%) in men and 49% (37% to 59%) in women. The observed decline was 55% (51% to 58%) and 68% (61 to 74) respectively. CONCLUSION: An assessment of the data on the risk factors for ischaemic heart disease and mortality suggests that most of the decline in mortality from ischaemic heart disease can be explained by changes in the three main coronary risk factors.

Adult↗

PubMed1995

Do changes in cardiovascular risk factors explain changes in mortality from stroke in Finland?

OBJECTIVES: To estimate the extent to which the changes in the main cardiovascular risk factors (blood pressure, smoking, and serum cholesterol concentration) can explain the observed changes in mortality from stroke in Finland during the past 20 years. DESIGN: Predicted changes in mortality from cerebrovascular disease mortality were calculated by a proportional hazards model from data obtained in cross sectional population surveys in 1972, 1977, 1982, 1987, and 1992. Predicted changes were compared with the observed changes in mortality statistics. SETTING: North Karelia and Kuopio provinces, Finland. SUBJECTS: 16,741 men and 16,389 women aged 30-59 randomly selected from the national population register, of whom 14,054 men and 14,546 women participated. MAIN OUTCOME MEASURES: Levels of risk factors and predicted and observed changes in mortality from cerebrovascular disease. RESULTS: The observed changes in diastolic blood pressure, total serum cholesterol concentration, and smoking in the population from 1972 to 1992 predicted a 44% fall in mortality from stroke in men and changes in diastolic blood pressure and smoking predicted a 34% fall in women. The observed fall in mortality from stroke was 66% in men and 60% in women. CONCLUSIONS: Two thirds of the fall in mortality from stroke in men and half in women can be explained by changes in the three main cardiovascular risk factors.

Adult↗

PubMed1999

Explaining variation in hospital admission rates between general practices: cross sectional study.

OBJECTIVES: To quantify the extent of the variation in hospital admission rates between general practices, and to investigate whether this variation can be explained by factors relating to the patient, the hospital, and the general practice. DESIGN: Cross sectional analysis of routine data. SETTING: Merton, Sutton, and Wandsworth Health Authority, which includes areas of inner and outer London. SUBJECTS: 209 136 hospital admissions in 1995-6 in patients registered with 120 general practices in the study area. MAIN OUTCOME MEASURES: Hospital admission rates for general practices for overall, emergency, and elective admissions. RESULTS: Crude admission rates for general practices displayed a twofold difference between the 10th and the 90th centile for all, emergency, and elective admissions. This difference was only minimally reduced by standardising for age and sex. Sociodemographic patient factors derived from census data accounted for 42% of the variation in overall admission rates; 45% in emergency admission rates; and 25% in elective admission rates. There was a strong positive correlation between factors related to deprivation and emergency, but not elective, admission rates, raising questions about equity of provision of health care. The percentage of each practice's admissions to different local hospitals added significantly to the explanation of variation, while the general practice characteristics considered added very little. CONCLUSIONS: Hospital admission rates varied greatly between general practices; this was largely explained by differences in patient populations. The lack of significant factors related to general practice is of little help for the direct management of admission rates, although the effect of sociological rather than organisational practice variables should be explored further. Admission rates should routinely be standardised for differences in patient populations and hospitals used.

Cross-Sectional Studies↗