Inguinal hernia repair among men: development and validation of a preoperative risk score for persistent postoperative pain.

PURPOSE: Persistent postoperative pain (PPP) is a prevalent complication after inguinal hernia repair. The aim of this study was to develop and validate a preoperative risk score for PPP. METHODS: We developed the risk score based on a cohort of 2,508 Danish men, who answered a questionnaire six months after inguinal hernia repair performed 2015-2016. PPP was defined as a numerical rating scale score ≥ 2 during activity six months postoperatively. Logistic regression analyses were undertaken to determine statistically significant predictors of PPP. Univariable analysis selected potential predictors with a p value ≤ 0.20, and a subsequent multivariable model was built using backward elimination with a criterion of p value < 0.10. We created a risk score based on the ß coefficients of the multivariable model. The risk score was validated internally using Hosmer-Lemeshow goodness of fit test, calibration belt test, and receiver operating characteristic curve analyses with 95% confidence intervals based on the bootstrap analysis. External validation was performed in a cohort of 293 men recruited preoperatively. RESULTS: Predictors of PPP were age 18-49 and 50-59 (versus ≥ 60) years (p < 0.001), total load lifted > 1,000 kg/day (p = 0.001), working in a bent-over position > 1 h/day (p < 0.001), leisure-time physical activity < 2 h/week (p = 0.009), increasing body mass index (per unit) (p < 0.003), and repair of recurrent hernia (p = 0.001).The preoperative risk score predicted risks of 6-61% in the development population. The model showed good internal and external validity. CONCLUSION: The results suggest that the risk of PPP after inguinal hernia repair can be predicted using a preoperative risk score.

Use of antihypertensive drugs and risk of skin cancer.

BACKGROUND: Several antihypertensive drugs are photosensitizing and may therefore act as cocarcinogens with ultraviolet radiation. OBJECTIVE: To examine whether antihypertensive drug use is associated with squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and malignant melanoma (MM). METHODS: We used population-based databases to conduct a case-control study including all first-time cases of SCC (n = 2282), BCC (n = 17,242), and MM (n = 3660) in northern Denmark, 1991-2010. We matched approximately 10 controls (n = 231,743) to each case by age, sex and county using risk-set sampling. We used conditional logistic regression to compute odds ratios (ORs) for skin cancer with 95% confidence intervals comparing ever users of antihypertensives (>2 previous prescriptions) with non-users (≤2 previous prescriptions). We adjusted for comorbidity and comedications. We further analysed use by duration (short term: <5 years; long term: ≥5 years) and intensity (low intensity or high intensity: <50% or ≥50% prescription coverage during total duration of use, respectively). RESULTS: Ever users of diuretics were at increased risk of SCC (OR 1.19; 1.06-1.33), driven by potassium-sparing agents alone (OR 1.40; 1.09-1.80) or with low-ceiling diuretics (OR 2.68; 2.24-3.21) and by long-term use (OR 1.41; 1.16-1.72 at low intensity; OR 1.44; 0.98-2.14 at high intensity). Ever users of sulphonamides (OR 1.49; 1.04-2.12) and non-aldosterone antagonist potassium-sparing agents (OR 2.26; 0.85-6.01) were at increased MM risk. The latter was also associated with BCC (OR 1.47; 1.00-2.17), as was low-ceiling diuretics combined with potassium-sparing agents (OR 1.23; 1.12-1.35). Long-term, low-intensity (OR 1.53; 1.05-2.23) and high-intensity (OR 1.44; 0.56-3.69) angiotensin receptor blocker use was associated with MM. Estimates for angiotensin-converting enzyme inhibitors, ß-blockers, and calcium channel blockers were inconsistent or weak (<20% increased). CONCLUSION: Long-term angiotensin receptor blocker use was associated with risk of MM. Moreover, long-term diuretic use was associated with SCC risk, driven by potassium-sparing agents alone or in combination with low-ceiling diuretics.

Dopamine transporter DAT and receptor DRD2 variants affect risk of lethal cocaine abuse: a gene-gene-environment interaction.

Epistatic gene-gene interactions could contribute to the heritability of complex multigenic disorders, but few examples have been reported. Here, we focus on the role of aberrant dopaminergic signaling, involving the dopamine transporter DAT, a cocaine target, and the dopamine D2 receptor, which physically interacts with DAT. Splicing polymorphism rs2283265 of DRD2, encoding D2 receptors, were shown to confer risk of cocaine overdose/death (odds ratio ∼3) in subjects and controls from the Miami Dade County Brain Bank.(1) Risk of cocaine-related death attributable to the minor allele of rs2283265 was significantly enhanced to OR=7.5 (P=0.0008) in homozygous carriers of the main 6-repeat allele of DAT rs3836790, a regulatory VNTR in intron8 lacking significant effect itself. In contrast, carriers of the minor 5-repeat DAT allele showed no significant risk (OR=1.1, P=0.84). DAT rs3836790 and DRD2 rs2283265 also interacted by modulating DAT protein activity in the ventral putamen of cocaine abusers. In high-linkage disequilibrium with the VNTR, DAT rs6347 in exon9 yielded similar results. Assessing the impact of DAT alone, a rare DAT haplotype formed by the minor alleles of rs3836790 and rs27072, a regulatory DAT variant in the 3'-UTR, occurred in nearly one-third of the cocaine abusers but was absent in African American controls, apparently conferring strong risk. These results demonstrate gene-gene-drug interaction affecting risk of fatal cocaine intoxication.

Association of gastrointestinal illness and recreational water exposure at an inland U.S. beach.

Recent epidemiology studies examining U.S. recreational water exposure and illness relationships have focused primarily on coastal and Great Lakes beaches. Human-made lakes in the U.S. have received little attention in epidemiology studies despite contributing to more waterborne disease epidemics annually than coastal U.S. waters. In a comprehensive beach cohort study, we examined relationships between water quality indicators and reported adverse health outcomes among users of a beach at an inland U.S. lake. Human health data was collected over 26 swimming days during the 2009 swimming season in conjunction with water quality measurements. Adverse health outcomes were reported 8-9 days post-exposure via a phone survey. Wading, playing or swimming in the water was observed to be a significant risk factor for GI illness (adjusted odds ratio (AOR) of 3.2; CI 1.1, 9.0). Among water users, Escherichia coli density was significantly associated with elevated GI illness risk where the highest E. coli quartile was associated with an AOR of 7.0 (CI 1.5, 32). GI illness associations are consistent with previous freshwater epidemiology studies. Our findings are unique in that our observations of positive associations with GI illness risk are based upon a single daily E. coli measurement. Lastly, this study focused on an understudied issue, illness risk at inland reservoirs. Our results support the usefulness of E. coli as a health-relevant indicator of water quality for this inland U.S. beach.

Therapy-related myelodysplasia and leukemia occur infrequently following VP-16 priming and autotransplantation without total body irradiation.

The use of VP-16 for stem cell mobilization has been cited as a significant risk factor for the development of therapy-related myelodysplasia/leukemia (tMDS/tAML) following autologous transplantation. The present study analyzed a large cohort of patients who underwent autotransplantation following stem cell mobilization with VP-16 and radiation-free preparation in order to determine the risk of tMDS/tAML. The estimated incidence of 9.9% at 7 years suggests that in the absence of TBI, VP-16 priming is not associated with an increased incidence of tMDS/tAML.

Demographic and phenotypic features of 70 families segregating Barrett's oesophagus and oesophageal adenocarcinoma.

BACKGROUND: Based on reported familial patterns, inheritance of a predisposition of developing Barrett's oesesophagus (BO) and oesophageal adenocarcinoma (OAC) likely follows an autosomal dominant model of most inherited cancer syndromes. oesophagus (BO) and oesophageal adenocarcinoma (OAC) likely follows an autosomal dominant model of most inherited cancer syndromes. AIMS: We analysed the phenotypic features of 70 familial BO/OAC families accrued for the purpose of initiating a linkage study to search for genes that contribute to susceptibility for BO/OAC. METHODS: Families with young or familial BO/OAC were recruited from participating institutions and self-referral from advertisement. RESULTS: A total of 70 families (173 affected and 784 unaffected individuals) were recruited into this study. Mean ages of diagnosis of BO and OAC among males were 50.6 and 57.4 years, respectively; among females, 52.1 and 63.5 years, respectively. The standardised incidence ratio (SIR) of cancers other than OAC or oesophagogastric junctional adenocarcinoma (OGJAC), among probands was 0.71. Seventy one percent of the pedigrees have "typical" structures with less than three affected individuals. Power calculations under realistic model assumptions suggest that if genetic heterogeneity is absent or limited, then DNA collection from members of these pedigrees could enable the identification of a novel candidate susceptibility gene for BO/OAC in a genome scan. CONCLUSIONS: This is the largest series of families with BO/OAC yet reported, features of which are consistent with inherited germline predisposition. Further, the SIR of cancers other than OAC/OGJAC was 0.71 among 70 probands, indicating these individuals were not more likely to develop non-OAC cancers.

Genetic model of multi-step breast carcinogenesis involving the epithelium and stroma: clues to tumour-microenvironment interactions.

Although numerous studies have reported that high frequencies of loss of heterozygosity (LOH) at various chromosomal arms have been identified in breast cancer, differential LOH in the neoplastic epithelial and surrounding stromal compartments has not been well examined. Using laser capture microdissection, which enables separation of neoplastic epithelium from surrounding stroma, we microdissected each compartment of 41 sporadic invasive adenocarcinomas of the breast. Frequent LOH was identified in both neoplastic epithelial and/or stromal compartments, ranging from 25 to 69% in the neoplastic epithelial cells, and from 17 to 61% in the surrounding stromal cells, respectively. The great majority of markers showed a higher frequency of LOH in the neoplastic epithelial compartment than in the stroma, suggesting that LOH in neoplastic epithelial cells might precede LOH in surrounding stromal cells. Furthermore, we sought to examine pair-wise associations of particular genetic alterations in either epithelial or stromal compartments. Seventeen pairs of markers showed statistically significant associations. We also propose a genetic model of multi-step carcinogenesis for the breast involving the epithelial and stromal compartments and note that genetic alterations occur in the epithelial compartments as the earlier steps followed by LOH in the stromal compartments. Our study strongly suggests that interactions between breast epithelial and stromal compartments might play a critical role in breast carcinogenesis and several genetic alterations in both epithelial and stromal compartments are required for breast tumour growth and progression.

Elevated blood pressure predicts the risk of acute rejection in renal allograft recipients.

BACKGROUND: Acute rejection (AR) is a strong predictor of renal allograft survival. Recent advances in immunosuppression have reduced considerably the incidence of AR. Still, approximately 25% of patients have AR early post-transplant, and the factors that predispose to AR have not been fully clarified. METHODS: The study includes 1641 adults, recipients of first cadaveric (CAD, N = 1195) or living related renal grafts (LRD, N = 446), transplanted in one institution. The variables associated with the occurrence of AR during the first year post-transplant were identified. RESULTS: By univariate analyses, AR was associated with the following variables: younger (P < 0.001); heavier (P = 0.003); and African American recipients (P = 0.002); CAD transplants (P = 0.001); higher number of HLA mismatches (P = 0.001); delayed graft function (DGF, P = 0.001); higher levels of serum creatinine post-transplant (P = 0.003); and higher levels of systolic and/or diastolic blood pressure (BP) post-transplant (P < 0.001). Higher BP levels were also associated with earlier AR episodes (P < 0.0001). By multivariable analysis AR was significantly associated with recipient age, number of HLA mismatches, DGF, pre-PRA and systolic BP. Analysis of BP measured weekly post-transplant indicated that elevated BP levels, even three weeks prior to the AR episode, were significantly associated with AR. For every level of BP, the use of BP medications was associated with a lower incidence of AR (P < 0.0001). Furthermore, the use of calcium channel blockers was also associated with lower incidence of AR (P = 0.001). Of note, 81% of recipients whose BP increased after the transplant had AR. In contrast, 22% of patients whose BP declined post-transplant had AR. CONCLUSIONS: Elevated BP levels post-transplant identify patients at high risk of AR independently of graft function. Treatment of BP and reduction of BP levels appears to be associated with a decreased risk of AR. We hypothesize that high BP may be an indicator of a particular type of allograft damage, perhaps ischemic, that may predispose to AR.

Delays in receipt of immunizations in low-birth-weight children: a nationally representative sample.

BACKGROUND: Studies of very low-birth-weight (VLBW) children discharged from neonatal intensive care units have shown delays in receipt of routine childhood immunizations. However, a recent study of VLBW children in 3 health maintenance organizations found no significant delays in immunizations. OBJECTIVE: To assess the risk of immunization delays for moderately low-birth-weight (MLBW; 1500 g-2499 g) and VLBW (<1500 g) children compared with normal-birth-weight children in a nationally representative birth sample. DESIGN: Logistic regression analysis using the 1988 National Maternal and Infant Health Survey and the 1991 Longitudinal Follow-up Survey. SETTING: Nationally representative sample of children born in 1988 in the United States. PARTICIPANTS: A total of 8285 children whose mothers completed both surveys. MAIN OUTCOME MEASURES: Age at receipt of each of the first 4 doses of diphtheria and tetanus toxoids and pertussis vaccine, the first 3 doses of polio vaccine, and the first dose of measles-mumps-rubella vaccine for MLBW and VLBW children, and normal-birth-weight children. We also examined whether children were up-to-date for all immunizations at ages 12, 24, and 36 months based on birth-weight groups. RESULTS: Very low-birth-weight children received their first 3 doses of diphtheria and tetanus toxoids and pertussis vaccine and their first 2 doses of polio vaccine significantly later than normal-birth-weight children (P <.001). Very low-birth-weight children were significantly less likely to be up to date for all immunizations at ages 12 months (odds ratio [OR] =.556; P =.001), 24 months (OR =.439; P <.001), and 36 months (OR =.446; P <.001) compared with normal-birth-weight children. CONCLUSION: Very low-birth-weight children are at risk for immunization delays compared with normal-birth-weight children.

Does cardioplegia type affect outcome and survival in patients with advanced left ventricular dysfunction? Results from the CABG Patch Trial.

BACKGROUND: There is controversy regarding which cardioplegic solution, temperature, and route of administration provides superior protection. The CABG Patch Trial enrolled a high-risk group of coronary artery disease patients with an ejection fraction of <36%. Thus, they constitute an ideal group to benefit most from optimal cardioplegic protection. METHODS AND RESULTS: All patients randomized into the trial were compared with respect to the use of blood and crystalloid cardioplegia. In addition, a questionnaire was sent to surgeons requesting blood cardioplegic temperature and route. Patients receiving crystalloid cardioplegia versus those receiving blood cardioplegia were found to have significantly more operative deaths (2% versus 0.3%, P:=0.02), postoperative myocardial infarctions (10% versus 2%, P:<0.001), shock (13% versus 7%, P:=0. 013), and postoperative conduction defects (21.6% versus 12.4%, P:=0. 001). Despite this, early death (6% crystalloid versus 4% blood cardioplegia) and late death (24% crystalloid versus 21% blood cardioplegia) statistics were not significantly different. Patients receiving normothermic blood had less postoperative right ventricular dysfunction (10%) than did patients receiving cold blood (25%) or cold blood with warm reperfusion (30%) (P:=0.004). There was no significant difference in early or late death. Finally, patients who received combined antegrade and retrograde cardioplegia had significantly less inotrope use (71% versus 84%, P:=0.002), right ventricular dysfunction (23% versus 41%, P:=0.001), and postoperative balloon pump use (12% versus 19%, P:=0.02) than did those who received antegrade cardioplegia. There was no difference in survival. CONCLUSIONS: Blood cardioplegia and combined antegrade and retrograde cardioplegia are superior to crystalloid and antegrade cardioplegia alone for postoperative morbidity. Despite this, there is no significant difference in early or late survival.

Patient characteristics and ICU organizational factors that influence frequency of pulmonary artery catheterization.

CONTEXT: Hemodynamic monitoring of patients with a pulmonary artery catheter is controversial because there are few data confirming its effectiveness, and patient and intensive care unit (ICU) organizational factors associated with its use are unknown. OBJECTIVE: To determine pulmonary artery catheter use in relationship to type of ICU organization and staffing, and patient characteristics, including severity of illness and insurance coverage. DESIGN, SETTING, AND PATIENTS: Retrospective database study of 10,217 nonoperative patients who received treatment at 34 medical, mixed medical and surgical, and surgical ICUs at 27 hospitals during 1998 (patients were enrolled in Project IMPACT). MAIN OUTCOME MEASURES: Pulmonary artery catheter use based on severity of illness measured by the Simplified Acute Physiology Score, resuscitation status at ICU admission, and ICU organizational variables, including type, size, and model. RESULTS: A pulmonary artery catheter was used for 831 patients (8.1%) in the ICU. In multivariate analysis adjusted for severity of illness, age, diagnosis, and do-not-resuscitate status, full-time ICU physician staffing was associated with a two-thirds reduction in the probability of catheter use (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.28-0.45). Higher catheter use was associated with white race (OR, 1.38; 95% CI, 1.10-1.72) and private insurance coverage (OR, 1.33; 95% CI, 1.10-1.60). Admission to a surgical ICU was associated with a 2-fold increase in probability of catheter use (OR, 2.17; 95% CI, 1.70-2.76) compared with either medical or mixed medical and surgical ICUs. CONCLUSION: Organizational characteristics of ICUs, insurance reimbursement, and race, as well as clinical variables, are associated with variation in practice patterns regarding pulmonary artery catheter use. Understanding such influences, combined with studies measuring clinical and economic outcomes, can contribute to the development of policies for the rational use of pulmonary artery catheters. JAMA. 2000;283:2559-2567

Practical considerations in the analysis of complex sample survey data.

Large scale sample surveys often provide fertile ground for analyses by epidemiologists. Recently, survey organizations such as the National Center for Health Statistics and the United States Bureau of the Census have distributed data from large surveys to interested investigators via CD-ROM. Confronted by the richness of such databases and the historic relative lack of availability of suitable software to appropriately account for the survey design, researchers have often simply ignored the complexities of the survey and analyzed the data as if they resulted from a simple random sample. The availability of modern programs such as STATA and SUDAAN provides data analysts with the new analytical capabilities to perform design-based analyses whenever appropriate. We used data from the NHANES III and the PAQUID study to illustrate the ease of performing design-based analyses. We also compared results of analyses under both model-based and design-based scenarios. When data from complex sample surveys were analyzed using both model-based and design-based strategies, differences in point estimates and standard errors of means, regression coefficients and odds ratios were found. The differences in regression coefficients and odds ratios between the two strategies were not as great as the differences in means. The potential for differences and the availability of survey analysis software should encourage researchers to use design-based techniques to analyze data from complex sample surveys more appropriately.

European system for cardiac operative risk evaluation (EuroSCORE).

OBJECTIVE: To construct a scoring system for the prediction of early mortality in cardiac surgical patients in Europe on the basis of objective risk factors. METHODS: The EuroSCORE database was divided into developmental and validation subsets. In the former, risk factors deemed to be objective, credible, obtainable and difficult to falsify were weighted on the basis of regression analysis. An additive score of predicted mortality was constructed. Its calibration and discrimination characteristics were assessed in the validation dataset. Thresholds were defined to distinguish low, moderate and high risk groups. RESULTS: The developmental dataset had 13,302 patients, calibration by Hosmer Lemeshow Chi square was (8) = 8.26 (P < 0.40) and discrimination by area under ROC curve was 0.79. The validation dataset had 1479 patients, calibration Chi square (10) = 7.5, P < 0.68 and the area under the ROC curve was 0.76. The scoring system identified three groups of risk factors with their weights (additive % predicted mortality) in brackets. Patient-related factors were age over 60 (one per 5 years or part thereof), female (1), chronic pulmonary disease (1), extracardiac arteriopathy (2), neurological dysfunction (2), previous cardiac surgery (3), serum creatinine >200 micromol/l (2), active endocarditis (3) and critical preoperative state (3). Cardiac factors were unstable angina on intravenous nitrates (2), reduced left ventricular ejection fraction (30-50%: 1, <30%: 3), recent (<90 days) myocardial infarction (2) and pulmonary systolic pressure >60 mmHg (2). Operation-related factors were emergency (2), other than isolated coronary surgery (2), thoracic aorta surgery (3) and surgery for postinfarct septal rupture (4). The scoring system was then applied to three risk groups. The low risk group (EuroSCORE 1-2) had 4529 patients with 36 deaths (0.8%), 95% confidence limits for observed mortality (0.56-1.10) and for expected mortality (1.27-1.29). The medium risk group (EuroSCORE 3-5) had 5977 patients with 182 deaths (3%), observed mortality (2.62-3.51), predicted (2.90-2.94). The high risk group (EuroSCORE 6 plus) had 4293 patients with 480 deaths (11.2%) observed mortality (10.25-12.16), predicted (10.93-11.54). Overall, there were 698 deaths in 14,799 patients (4.7%), observed mortality (4.37-5.06), predicted (4.72-4.95). CONCLUSION: EuroSCORE is a simple, objective and up-to-date system for assessing heart surgery, soundly based on one of the largest, most complete and accurate databases in European cardiac surgical history. We recommend its widespread use.

Illustration of analysis taking into account complex survey considerations: the association between wine consumption and dementia in the PAQUID study. Personnes Ages Quid.

Epidemiologists are increasingly looking to large-scale sample surveys to provide data for studies of the associations between known or suspected risk factors and disease. More often than not, widely available statistical software packages have been used to analyze such data, particularly when multivariable modeling is involved. Such packages assume that the data have resulted from simple random samples. However, when the survey design incorporates such features as clustering and stratification, the results of statistical analyses based on this assumption can be incorrect. The authors utilized data from the PAQUID (Personnes Agees Quid) study, collected periodically from 1988 to 1996, to illustrate the ease of performing a "design-based" (vs. a "model-based") analysis of complex survey data, and they compared the results obtained using both approaches. The PAQUID study is a stratified cluster sample of elderly community residents in the southwestern departments of Gironde and Dordogne, France. In the illustration presented-in which 3,777 community residents aged 65 years or older were selected to permit identification of baseline and lifetime factors that might be related to cognitive loss, dementia, and Alzheimer's disease--measures of association (such as odds ratios and their associated standard errors) were comparable for both analytical strategies. However, this may not be the case for other examples. Descriptive measures (such as estimates of means and proportions) may be more seriously compromised by the decision to ignore the sampling design. The availability of modern statistical packages with survey analysis capabilities should encourage data analysts to perform design-based analyses whenever possible.

Multicenter outcome study of cancer patients admitted to the intensive care unit: a probability of mortality model.

PURPOSE: To develop prospectively and validate a model for probability of hospital survival at admission to the intensive care unit (ICU) of patients with malignancy. PATIENTS AND METHODS: This was an inception cohort study in the setting of four ICUs of academic medical centers in the United States. Defined continuous and categorical variables were collected on consecutive patients with cancer admitted to the ICU. A preliminary model was developed from 1,483 patients and then validated on an additional 230 patients. Multiple logistic regression modeling was used to develop the models and subsequently evaluated by goodness-of-fit and receiver operating characteristic (ROC) analysis. The main outcome measure was hospital survival after ICU admission. RESULTS: The observed hospital mortality rate was 42%. Continuous variables used in the ICU admission model are PaO2/FiO2 ratio, platelet count, respiratory rate, systolic blood pressure, and days of hospitalization pre-ICU. Categorical entries include presence of intracranial mass effect, allogeneic bone marrow transplantation, recurrent or progressive cancer, albumin less than 2.5 g/dL, bilirubin > or = 2 mg/dL, Glasgow Coma Score less than 6, prothrombin time greater than 15 seconds, blood urea nitrogen (BUN) greater than 50 mg/dL, intubation, performance status before hospitalization, and cardiopulmonary resuscitation (CPR). The P values for the fit of the preliminary and validation models are .939 and .314, respectively, and the areas under the ROC curves are .812 and .802. CONCLUSION: We report a disease-specific multivariable logistic regression model to estimate the probability of hospital mortality in a cohort of critically ill cancer patients admitted to the ICU. The model consists of 16 unambiguous and readily available variables. This model should move the discussion regarding appropriate use of ICU resources forward. Additional validation in a community hospital setting is warranted.

A comparison of goodness-of-fit tests for the logistic regression model.

Recent work has shown that there may be disadvantages in the use of the chi-square-like goodness-of-fit tests for the logistic regression model proposed by Hosmer and Lemeshow that use fixed groups of the estimated probabilities. A particular concern with these grouping strategies based on estimated probabilities, fitted values, is that groups may contain subjects with widely different values of the covariates. It is possible to demonstrate situations where one set of fixed groups shows the model fits while the test rejects fit using a different set of fixed groups. We compare the performance by simulation of these tests to tests based on smoothed residuals proposed by le Cessie and Van Houwelingen and Royston, a score test for an extended logistic regression model proposed by Stukel, the Pearson chi-square and the unweighted residual sum-of-squares. These simulations demonstrate that all but one of Royston's tests have the correct size. An examination of the performance of the tests when the correct model has a quadratic term but a model containing only the linear term has been fit shows that the Pearson chi-square, the unweighted sum-of-squares, the Hosmer-Lemeshow decile of risk, the smoothed residual sum-of-squares and Stukel's score test, have power exceeding 50 per cent to detect moderate departures from linearity when the sample size is 100 and have power over 90 per cent for these same alternatives for samples of size 500. All tests had no power when the correct model had an interaction between a dichotomous and continuous covariate but only the continuous covariate model was fit. Power to detect an incorrectly specified link was poor for samples of size 100. For samples of size 500 Stukel's score test had the best power but it only exceeded 50 per cent to detect an asymmetric link function. The power of the unweighted sum-of-squares test to detect an incorrectly specified link function was slightly less than Stukel's score test. We illustrate the tests within the context of a model for factors associated with low birth weight.