RESUMO
BACKGROUND: A dedicated operating team is defined as a surgical team consisting of the same group of people working together over time, optimally attuned in both technical and/or communicative aspects. This can be achieved through technical and/or communicative training in a team setting. A dedicated surgical team may contribute to the optimization of healthcare quality and patient safety within the perioperative period. METHOD: A systematic review was conducted to evaluate the effects of a dedicated surgical team on clinical and performance outcomes. MEDLINE and Embase were searched on 23 June 2022. Both randomized controlled trials (RCTs) and non-randomized studies (NRSs) were included. Primary outcomes were mortality, complications and readmissions. Secondary outcomes were costs and performance measures. RESULTS: Fourteen studies were included (RCTs n = 1; NRSs n = 13). Implementation of dedicated operating teams was associated with improvements in mortality, turnover time, teamwork, communication and costs. No significant differences were observed in readmission rates and length of hospital stay. Results regarding duration, glitch counts and complications of surgery were inconclusive. Limitations include study conduct and heterogeneity between studies. CONCLUSIONS: The institution of surgical teams who followed communicative and/or technical training appeared to have beneficial effects on several clinical outcome measures. Dedicated teams provide a feasible way of improving healthcare quality and patient safety. A dose-response effect of team training was reported, but also a relapse rate, suggesting that repetitive training is of major concern to high-quality patient care. Further studies are needed to confirm these findings, due to limited level of evidence in current literature. PROSPERO REGISTRATION NUMBER: CRD42020145288.
Assuntos
Comunicação , Equipe de Assistência ao Paciente , Humanos , Tempo de Internação , Qualidade da Assistência à Saúde , Segurança do PacienteRESUMO
BACKGROUND AND AIMS: Eosinopenia is a marker for acute inflammation. We hypothesized that eosinopenia at Intensive Care Unit (ICU) admission in vascular surgery patients who receive critical care, would be associated with increased mortality following hospital discharge. METHODS AND RESULTS: We performed a two-center observational cohort study of critically ill, non-cardiac adult vascular surgery patients who received treatment in Boston between 1997 and 2012 and survived hospital admission. The consecutive sample included 5083 patients (male 57%, white 82%, mean age [SD] 61.6 [17.4] years). The exposure was Absolute eosinophil count measured within 24 h of admission to the ICU and categorized as ≤10 cells/µL, 11-50 cells/µL, 51-100 cells/µL, 101-350 cells/µL (normal range), and >350 cells/µL. The primary outcome was all-cause mortality within 90 days of hospital discharge. The secondary outcome was discharge to home following hospitalization. 90-day post-discharge mortality was 6.7%, and 12.9% of patients were readmitted within 30 days. After multivariable adjustment, patients with eosinopenia (≤10 cells/µL) have a 90-day post-discharge mortality OR of 1.97 (95%CI 1.42, 2.73; P < 0.001) relative to patients with an absolute eosinophil count of 101-350 cells/µL. Further, after multivariable adjustment, patients with eosinopenia (≤10 cells/µL) have a 25% lower odds of discharge to home compared to patients with an absolute eosinophil count of 101-350 cells/µL [OR = 0.71 (CI 95% 0.59-0.85); P < 0.001]. CONCLUSION: Eosinopenia at ICU admission is a robust predictor of increased mortality and lower likelihood of discharge to home in vascular surgery patients treated with critical care who survive hospitalization.
Assuntos
Eosinófilos , Doenças Vasculares/cirurgia , Procedimentos Cirúrgicos Vasculares , Idoso , Idoso de 80 Anos ou mais , Boston , Estado Terminal , Feminino , Humanos , Contagem de Leucócitos , Masculino , Pessoa de Meia-Idade , Alta do Paciente , Valor Preditivo dos Testes , Medição de Risco , Fatores de Risco , Fatores de Tempo , Resultado do Tratamento , Doenças Vasculares/sangue , Doenças Vasculares/diagnóstico , Doenças Vasculares/mortalidade , Procedimentos Cirúrgicos Vasculares/efeitos adversos , Procedimentos Cirúrgicos Vasculares/mortalidadeRESUMO
OBJECTIVE: The decision whether or not to proceed with surgical intervention of a patient with a ruptured abdominal aortic aneurysm (rAAA) is very difficult in daily practice. The primary objective of the present study was to develop and to externally validate a new prediction model: the Dutch Aneurysm Score (DAS). METHODS: With a prospective cohort of 10 hospitals (n = 508) the DAS was developed using a multivariate logistic regression model. Two retrospective cohorts with rAAA patients from two hospitals (n = 373) were used for external validation. The primary outcome was the combined 30 day and in-hospital death rate. Discrimination (AUC), calibration plots, and the ability to identify high risk patients were compared with the more commonly used Glasgow Aneurysm Score (GAS). RESULTS: After multivariate logistic regression, four pre-operative variables were identified: age, lowest in hospital systolic blood pressure, cardiopulmonary resuscitation, and haemoglobin level. The area under the receiver operating curve (AUC) for the DAS was 0.77 (95% CI 0.72-0.82) compared with the GAS with an AUC of 0.72 (95% CI 0.67-0.77). The DAS showed a death rate in patients with a predicted death rate ≥80% of 83%. CONCLUSIONS: The present study shows that the DAS has a higher discriminative performance (AUC) compared with the GAS. All clinical variables used for the DAS are easy to obtain. Identification of low risk patients with the DAS can potentially reduce turndown rates. The DAS can reliably be used by clinicians to make a more informed decision in dialogue with the patient and their family whether or not to proceed with surgical intervention.
Assuntos
Aneurisma da Aorta Abdominal/cirurgia , Ruptura Aórtica/cirurgia , Técnicas de Apoio para a Decisão , Procedimentos Cirúrgicos Vasculares/mortalidade , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Aneurisma da Aorta Abdominal/diagnóstico , Aneurisma da Aorta Abdominal/mortalidade , Ruptura Aórtica/diagnóstico , Ruptura Aórtica/mortalidade , Área Sob a Curva , Biomarcadores/sangue , Pressão Sanguínea , Reanimação Cardiopulmonar/mortalidade , Feminino , Escala de Coma de Glasgow , Hemoglobinas/metabolismo , Mortalidade Hospitalar , Humanos , Modelos Logísticos , Masculino , Análise Multivariada , Países Baixos , Valor Preditivo dos Testes , Estudos Prospectivos , Curva ROC , Reprodutibilidade dos Testes , Estudos Retrospectivos , Medição de Risco , Fatores de Risco , Fatores de Tempo , Resultado do Tratamento , Procedimentos Cirúrgicos Vasculares/efeitos adversosRESUMO
BACKGROUND: A substantial proportion of patients with a ruptured abdominal aortic aneurysm (rAAA) die outside hospital. The objective of this study was to estimate the total mortality, including prehospital deaths, of patients with rAAA. METHODS: This was a systematic review and meta-analysis following the MOOSE guidelines. The Embase, MEDLINE and Cochrane Library databases were searched. All population-based studies reporting both prehospital and in-hospital mortality in patients with rAAA were included. Studies were assessed for methodological quality and heterogeneity, and pooled estimates of mortality from rAAA were calculated using a random-effects model. RESULTS: From a total of 3667 studies, 24 retrospective cohort studies, published between 1977 and 2012, met the inclusion criteria. The quality of included studies varied, in particular the method of determining prehospital deaths from rAAA. The estimated pooled total mortality rate was 81 (95 per cent confidence interval 78 to 83) per cent. A decline in mortality was observed over time (P = 0·002); the pooled estimate of total mortality in high-quality studies before 1990 was 86 (83 to 89) per cent, compared with 74 (72 to 77) per cent since 1990. Some 32 (27 to 37) per cent of patients with rAAA died before reaching hospital. The in-hospital non-intervention rate was 40 (33 to 47) per cent, which also declined over the years. CONCLUSION: The pooled estimate of total mortality from rAAA is very high, although it has declined over the years. Most patients die outside hospital, and there is no surgical intervention in a considerable number of those who survive to reach hospital.
Assuntos
Aneurisma da Aorta Abdominal/mortalidade , Ruptura Aórtica/mortalidade , Idoso , Aneurisma da Aorta Abdominal/cirurgia , Ruptura Aórtica/cirurgia , Serviços Médicos de Emergência/estatística & dados numéricos , Feminino , Humanos , Masculino , Assistência Perioperatória/mortalidade , Estudos Retrospectivos , Taxa de SobrevidaRESUMO
BACKGROUND: Malnutrition is often present in vascular surgery patient during hospital admission. The present evidence of the consequence malnutrition has on morbidity and mortality is limited. AIM: The purpose of this study was to determine the effect of nutritional status on out-of-hospital mortality in vascular surgery patients. METHODS: An observational cohort study was performed, studying non-cardiac vascular surgery patients surviving hospital admission 18 years or older treated in Boston, Massachusetts, USA. The exposure of interest was nutritional status categorized as well nourished, at-risk for malnutrition, nonspecific malnutrition or protein-energy malnutrition. The all cause 90-day mortality following hospital discharge was the primary outcome. Adjusted odds ratios were estimated by multivariable logistic regression models. RESULTS: This cohort included 4432 patients comprised of 48% women and a mean age 61.7 years. After evaluation by a registered dietitian, 3819 patients were determined to be well nourished, 215 patients were at-risk for malnutrition, 351 had non-specific malnutrition and 47 patients had protein-energy malnutrition. After adjustment for age, sex, ethnicity, medical versus surgical Diagnosis Related Group type, Deyo-Charlson index, length of stay, and vascular Current Procedural Terminology code category, the 90-day post-discharge mortality odds ratio for patients with non-specific malnutrition OR 1.96 (95%CI 1.21, 3.17) and for protein-energy malnutrition OR 3.58 (95%CI 1.59, 8.06), all relative to patients without malnutrition. DISCUSSION: Nutritional status is a strong predictor of out-of-hospital mortality. This suggests that patient with vascular disease suffering from malnutrition could benefit from more intensified In-hospital and out-of-hospital dietary guidance and interventions.
Assuntos
Desnutrição , Desnutrição Proteico-Calórica , Assistência ao Convalescente , Estado Terminal , Feminino , Mortalidade Hospitalar , Humanos , Tempo de Internação , Masculino , Desnutrição/diagnóstico , Pessoa de Meia-Idade , Avaliação Nutricional , Estado Nutricional , Alta do Paciente , Fatores de Risco , Procedimentos Cirúrgicos VascularesRESUMO
Targeted maximum likelihood methodology is applied to provide a test that makes use of the covariate data that are commonly collected in randomized trials, and does not require assumptions beyond those of the logrank test when censoring is uninformative. Under informative censoring, the logrank test is biased, whereas the test provided in this article is consistent under consistent estimation of the censoring mechanism or the conditional hazard for survival. Two approaches based on this methodology are provided: (1) a substitution-based approach that targets treatment and time-specific survival from which the logrank parameter is estimated, and (2) directly targeting the logrank parameter.
Assuntos
Interpretação Estatística de Dados , Funções Verossimilhança , Ensaios Clínicos Controlados Aleatórios como Assunto/estatística & dados numéricos , Algoritmos , Simulação por Computador , HumanosRESUMO
Pericardial cysts are rare but well recognized tumors of the mediastinum. Most pericardial cysts are located in the right or left cardiophrenic angle. At other locations these cysts may pose a diagnostic problem. We present two cases of an atypically located pericardial cyst and a short review of the literature.
Assuntos
Cisto Mediastínico/cirurgia , Mediastino , Timoma/cirurgia , Neoplasias do Timo/cirurgia , Adulto , Humanos , Masculino , Cisto Mediastínico/diagnóstico , Pessoa de Meia-Idade , Pericardiectomia , Timoma/diagnóstico , Neoplasias do Timo/diagnóstico , Resultado do TratamentoRESUMO
This article is devoted to the construction and asymptotic study of adaptive group sequential covariate-adjusted randomized clinical trials analyzed through the prism of the semipara-metric methodology of targeted maximum likelihood estimation (TMLE). We show how to build, as the data accrue group-sequentially, a sampling design which targets a user-supplied optimal design. We also show how to carry out a sound TMLE statistical inference based on such an adaptive sampling scheme (therefore extending some results known in the i.i.d setting only so far), and how group-sequential testing applies on top of it. The procedure is robust (i.e., consistent even if the working model is misspecified). A simulation study confirms the theoretical results, and validates the conjecture that the procedure may also be efficient.
RESUMO
OBJECTIVE: This study quantifies the effects of leisure-time physical activity (LTPA) on walking speed independently of body composition in an elderly cohort, and in those elderly with metabolic derangements due to age, diabetes, and cardiovascular disease (CVD). METHODS: 1655 community-dwelling women and men >55 years were measured for body composition (lean mass : fat mass ratio, LNFAT) , based on estimated bioelectric impedance by using population-specific prediction equations derived from dual-energy x-ray absorptiometry. In addition to LNFAT, LTPA, diabetes, CVD, walking speed, and other covariates were measured biannually over an 8-year period. LTPA was categorized as <22.5 Mets/week, ≥ 22.5 Mets/week, based on public-health recommended guidelines, and LNFAT was dichotomized based on its sex-specific median. Direct effects of high vs. low LTPA on walking speed were estimated for fixed levels of LNFAT, which represented an intermediary variable in the analysis. Stratified estimates of effects were obtained using subject status (e.g., age≥75 years, diabetes, CVD) at each visit. RESULTS: Walking speed was significantly greater (0.74, 0.75 m/s in women and men, respectively) if subjects experienced LTPA ≥22.5 Mets/week and > median LNFAT, compared with <22.5 Mets/week and ≤ median LNFAT (0.68, 0.69 m/s). While direct effects of LTPA contributed to higher walking speed, none were significant in the overall, nor the stratified groups of subjects, of either sex. CONCLUSIONS: Walking speed increases with greater LTPA and LNFAT in the elderly, but there was no evidence to indicate that walking speed increases from LTPA independently of body composition and the metabolic processes it represents.
Assuntos
Exercício Físico/fisiologia , Atividades de Lazer , Esforço Físico/fisiologia , Aptidão Física/fisiologia , Idoso , Envelhecimento/metabolismo , Composição Corporal , Doenças Cardiovasculares/metabolismo , Estudos de Coortes , Diabetes Mellitus/metabolismo , Feminino , Avaliação Geriátrica , Humanos , Masculino , Equivalente Metabólico , Pessoa de Meia-Idade , CaminhadaRESUMO
It is a challenge to evaluate experimental treatments where it is suspected that the treatment effect may only be strong for certain subpopulations, such as those having a high initial severity of disease, or those having a particular gene variant. Standard randomized controlled trials can have low power in such situations. They also are not optimized to distinguish which subpopulations benefit from a treatment. With the goal of overcoming these limitations, we consider randomized trial designs in which the criteria for patient enrollment may be changed, in a preplanned manner, based on interim analyses. Since such designs allow data-dependent changes to the population enrolled, care must be taken to ensure strong control of the familywise Type I error rate. Our main contribution is a general method for constructing randomized trial designs that allow changes to the population enrolled based on interim data using a prespecified decision rule, for which the asymptotic, familywise Type I error rate is strongly controlled at a specified level α. As a demonstration of our method, we prove new, sharp results for a simple, two-stage enrichment design. We then compare this design to fixed designs, focusing on each design's ability to determine the overall and subpopulation-specific treatment effects.
RESUMO
Covariate adjustment using linear models for continuous outcomes in randomized trials has been shown to increase efficiency and power over the unadjusted method in estimating the marginal effect of treatment. However, for binary outcomes, investigators generally rely on the unadjusted estimate as the literature indicates that covariate-adjusted estimates based on the logistic regression models are less efficient. The crucial step that has been missing when adjusting for covariates is that one must integrate/average the adjusted estimate over those covariates in order to obtain the marginal effect. We apply the method of targeted maximum likelihood estimation (tMLE) to obtain estimators for the marginal effect using covariate adjustment for binary outcomes. We show that the covariate adjustment in randomized trials using the logistic regression models can be mapped, by averaging over the covariate(s), to obtain a fully robust and efficient estimator of the marginal effect, which equals a targeted maximum likelihood estimator. This tMLE is obtained by simply adding a clever covariate to a fixed initial regression. We present simulation studies that demonstrate that this tMLE increases efficiency and power over the unadjusted method, particularly for smaller sample sizes, even when the regression model is mis-specified.
Assuntos
Funções Verossimilhança , Modelos Lineares , Ensaios Clínicos Controlados Aleatórios como Assunto/estatística & dados numéricos , Humanos , Resultado do TratamentoRESUMO
AIM: The aim of study was to compare the sensitivity of MRI and CTA for endoleak detection and classification after EVAR. PATIENTS & METHODS: Twenty-eight patients, between 2 days and 65 months after EVAR, were evaluated with both CT and MRI. Twenty-five patients had an Ancure graft and the other three had an Excluder. The MRI protocol for endoleak evaluation included: a T1-weighted spin echo, a high-resolution 3D CE-MRA, and a post-contrast T1-weighted spin echo. In total 40 ml Gadolinium was administered. The CT protocol consisted of a blank survey followed by a spiral CT angiography (CTA) using 140 ml of Ultravist. An experienced, blinded observer evaluated all CTs and MRIs. RESULTS: Using MRI and MRA techniques significantly more endoleaks (23/35) were detected than with CTA (11/35) (p=0.01, Chi-Square). CT could not determine the type of endoleak in 3 of the 11 endoleaks detected and was uncertain in one. MRI was uncertain about the type in 14 of the 23 endoleaks detected. All endoleaks visible on CT were visible by MRI as well. CONCLUSIONS: MRI techniques are more sensitive for the detection of endoleak after endovascular AAA repair than CT.
Assuntos
Angioplastia , Aneurisma da Aorta Abdominal/cirurgia , Imageamento por Ressonância Magnética , Complicações Pós-Operatórias/diagnóstico , Tomografia Computadorizada por Raios X , Idoso , Idoso de 80 Anos ou mais , Aneurisma da Aorta Abdominal/diagnóstico , Aneurisma da Aorta Abdominal/diagnóstico por imagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Sensibilidade e EspecificidadeRESUMO
AIM: To evaluate the value of dynamic contrast enhanced magnetic resonance angiography (CE-MRA) for classification of endoleaks after endovascular aneurysm repair (EVAR). MATERIALS AND METHODS: Twenty-eight patients, between 2 days and 54 months after EVAR, were evaluated with CTA, MRI and dynamic CE-MRA. The additional diagnostic value of the dynamic 3D CE-MRA was evaluated by determining the ability of the dynamic series in pinpointing the site of inflow of an endoleak. RESULTS: An endoleak was detected in 23 patients. Seventeen of the 23 dynamic series were technically successful (no disturbing artifacts limiting the diagnostic value). Using MRI our findings were: 2 type I, 6 type II, 1 type III, no type IV endoleaks and in 14 cases classification could not be made. The classification results for MRI plus the dynamic CE-MRA were: 2 type I, 12 type II, 1 type III, no type IV endoleaks and in eight cases classification could not be made. In six cases the dynamic MRA allowed classification of the endoleak, which was not possible with the non-dynamic images alone (p=0.091, Fisher exact). CONCLUSION: This pilot study shows that dynamic CE-MRA can have additional value in the classification of endoleaks. Dynamic CE-MRA might obviate the need for diagnostic digital subtraction angiography and aid planning for intervention.
Assuntos
Aneurisma da Aorta Abdominal/cirurgia , Meios de Contraste , Gadolínio DTPA , Angiografia por Ressonância Magnética , Complicações Pós-Operatórias/diagnóstico , Idoso , Idoso de 80 Anos ou mais , Aneurisma da Aorta Abdominal/diagnóstico , Aortografia , Implante de Prótese Vascular , Feminino , Humanos , Imageamento Tridimensional , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios XRESUMO
We derive an identity for nonparametric maximum likelihood estimators (NPMLE) and regularized MLEs in censored data models which expresses the standardized maximum likelihood estimators in terms of the standardized empirical process. This identity provides an effective starting point in proving both consistency and efficiency of NPMLE and regularized MLE. The identity and corresponding method for proving efficiency is illustrated for the NPMLE in the univariate right-censored data model, the regularized MLE in the current status data model and for an implicit NPMLE based on a mixture of right-censored and current status data. Furthermore, a general algorithm for estimation of the limiting variance of the NPMLE is provided.
Assuntos
Funções Verossimilhança , Algoritmos , Intervalos de Confiança , Interpretação Estatística de Dados , Infecções por HIV/transmissão , Humanos , Tábuas de VidaRESUMO
In this paper we build on previous work for estimation of the bivariate distribution of the time variables T1 and T2 when they are observable only on the condition that one of the time variables, say T1, is greater than (left-truncation) or less than (right truncation) some observed time variable C1. In this paper, we introduce several results based on the Influence Curve (which we derive in this paper) of the NPMLE of the distribution F of (T1, T2) developed by van der Laan (van der Laan, 1996). Specifically we will: prove that the NPMLE is asymptotically equivalent to an estimator developed by Gürler (Gürler, 1997), derive the asymptotic distribution of the NPMLE based on its Influence Curve, present tests to determine the amount of dependence between T1 and T2, present the results of simulation studies that compare the NPMLE and Gürler's estimator and evaluate the performance of both the above mentioned tests and confidence intervals of F based on the asymptotic distribution of the NPMLE, and finally we will apply the methods in a data analysis in which we also point out practical issues that arise in the implementation of the estimator.
Assuntos
Modelos Estatísticos , Análise Multivariada , Análise de Sobrevida , Síndrome da Imunodeficiência Adquirida/epidemiologia , Síndrome da Imunodeficiência Adquirida/etiologia , Humanos , Funções Verossimilhança , Estatísticas não Paramétricas , Fatores de Tempo , Reação TransfusionalRESUMO
In biostatistical applications interest often focuses on the estimation of the distribution of time T between two consecutive events. If the initial event time is observed and the subsequent event time is only known to be larger or smaller than an observed monitoring time C, then the data conforms to the well understood singly-censored current status model, also known as interval censored data, case I. Additional covariates can be used to allow for dependent censoring and to improve estimation of the marginal distribution of T. Assuming a wrong model for the conditional distribution of T, given the covariates, will lead to an inconsistent estimator of the marginal distribution. On the other hand, the nonparametric maximum likelihood estimator of FT requires splitting up the sample in several subsamples corresponding with a particular value of the covariates, computing the NPMLE for every subsample and then taking an average. With a few continuous covariates the performance of the resulting estimator is typically miserable. In van der Laan, Robins (1996) a locally efficient one-step estimator is proposed for smooth functionals of the distribution of T, assuming nothing about the conditional distribution of T, given the covariates, but assuming a model for censoring, given the covariates. The estimators are asymptotically linear if the censoring mechanism is estimated correctly. The estimator also uses an estimator of the conditional distribution of T, given the covariates. If this estimate is consistent, then the estimator is efficient and if it is inconsistent, then the estimator is still consistent and asymptotically normal. In this paper we show that the estimators can also be used to estimate the distribution function in a locally optimal way. Moreover, we show that the proposed estimator can be used to estimate the distribution based on interval censored data (T is now known to lie between two observed points) in the presence of covariates. The resulting estimator also has a known influence curve so that asymptotic confidence intervals are directly available. In particular, one can apply our proposal to the interval censored data without covariates. In Geskus (1992) the information bound for interval censored data with two uniformly distributed monitoring times at the uniform distribution (for T) has been computed. We show that the relative efficiency of our proposal w.r.t. this optimal bound equals 0.994, which is also reflected in finite sample simulations. Finally, the good practical performance of the estimator is shown in a simulation study.
Assuntos
Tábuas de Vida , Análise de Variância , Biometria , Interpretação Estatística de Dados , Humanos , Análise de Sobrevida , Fatores de TempoRESUMO
Recent developments in microarray technology make it possible to capture the gene expression profiles for thousands of genes at once. With this data researchers are tackling problems ranging from the identification of 'cancer genes' to the formidable task of adding functional annotations to our rapidly growing gene databases. Specific research questions suggest patterns of gene expression that are interesting and informative: for instance, genes with large variance or groups of genes that are highly correlated. Cluster analysis and related techniques are proving to be very useful. However, such exploratory methods alone do not provide the opportunity to engage in statistical inference. Given the high dimensionality (thousands of genes) and small sample sizes (often <30) encountered in these datasets, an honest assessment of sampling variability is crucial and can prevent the over-interpretation of spurious results. We describe a statistical framework that encompasses many of the analytical goals in gene expression analysis; our framework is completely compatible with many of the current approaches and, in fact, can increase their utility. We propose the use of a deterministic rule, applied to the parameters of the gene expression distribution, to select a target subset of genes that are of biological interest. In addition to subset membership, the target subset can include information about relationships between genes, such as clustering. This target subset presents an interesting parameter that we can estimate by applying the rule to the sample statistics of microarray data. The parametric bootstrap, based on a multivariate normal model, is used to estimate the distribution of these estimated subsets and relevant summary measures of this sampling distribution are proposed. We focus on rules that operate on the mean and covariance. Using Bernstein's Inequality, we obtain consistency of the subset estimates, under the assumption that the sample size converges faster to infinity than the logarithm of the number of genes. We also provide a conservative sample size formula guaranteeing that the sample mean and sample covariance matrix are uniformly within a distance epsilon > 0 of the population mean and covariance. The practical performance of the method using a cluster-based subset rule is illustrated with a simulation study. The method is illustrated with an analysis of a publicly available leukemia data set.