Biomedical subjects

I Van der Tweel

Publications and source records attributed to I Van der Tweel.

6 recordsLinked to original sources

PubMed2004

Salivary gland carcinoma: independent prognostic factors for locoregional control, distant metastases, and overall survival: results of the Dutch head and neck oncology cooperative group.

BACKGROUND: We analyzed the records of patients with malignant salivary gland tumors, as diagnosed in centers of the Dutch Head and Neck Oncology Cooperative Group, in search of independent prognostic factors for locoregional control, distant metastases, and overall survival. METHODS: In 565 patients, we analyzed general results and looked for the potential prognostic variables of age, sex, delay, clinical and pathologic T and N stage, site (332 parotid, 76 submandibular, 129 oral cavity, 28 pharynx/larynx), pain, facial weakness, clinical and pathologic skin involvement, histologic type (WHO 1972 classification), treatment, resection margins, spill, perineural and vascular invasion, number of neck nodes, and extranodal disease. The median follow-up period was 74 months; it was 99 months for patients who were alive on the last follow-up. RESULTS: The rates of local control, regional control, distant metastasis-free and overall survival after 10 years were, respectively, 78%, 87%, 67%, and 50%. In multivariable analysis, local control was predicted by clinical T-stage, bone invasion, site, resection margin, and treatment. Regional control depended on N stage, facial nerve paralysis, and treatment. The relative risk with surgery alone, compared to surgery plus postoperative radiotherapy, was 9.7 for local recurrence and 2.3 for regional recurrence. Distant metastases were independently correlated with T and N stage, sex, perineural invasion, histologic type, and clinical skin involvement. Overall survival depended on age, sex, T and pN stage, site, skin and bone invasion. CONCLUSIONS: Several prognostic factors for locoregional control, distant metastases, and overall survival were found. Postoperative radiotherapy was found to improve locoregional control.

Adenocarcinoma↗

PubMed2000

Sequential analysis of matched dichotomous data from prospective case-control studies.

Sequential analysis of randomized controlled clinical trials and epidemiological prospective (matched) case-control studies can have ethical or economical advantages above a fixed sample size approach. It offers the possibility to stop early when enough evidence for an apparent effect of the risk factor or lack of the expected effect is achieved. In clinical trials it is well accepted to stop the trial early in favour of the alternative hypothesis. In epidemiological studies, in general, the need is not felt to stop early in case of a clear exposure effect. Little attention has been paid, however, to early stopping and accepting the null hypothesis. In metabolic epidemiological studies, where analysis destroys the biological material, the question of efficient use of samples, for example, those stored in a biobank, becomes crucial. Also a slow accrual of cases or the costs of follow-up of a cohort nested study can make it desirable to stop a study early once it becomes clear that no relevant exposure effect will be found. Matching can further reduce the amount of information necessary to reach a conclusion. We derived test statistics Z (efficient score) and V (Fisher's information) for the sequential analysis of studies with dichotomous data where each case can be matched to one or more controls. A variable matching ratio is allowed. These test statistics can be entered into the software PEST to monitor the course of the study. The double sequential probability ratio test and the double triangular test were evaluated with simulated data for odds ratios equal to 1.5, 2.0 and 2.5 and various type I and type II error probabilities both under H(0) and under H(1). Our simulations resulted in average and median values for the amount of information (V) that are far less than those for a fixed sample size study. Efficiency gain ranges from 32 per cent to 60 per cent. The proposed sequential analysis was applied in an investigation on the possible relationship between the polymorphism of the MTHFR-gene and rectal cancer in a cohort of women with cases matched by age to one and to three controls. A sequential analysis of matched data can lead to early stopping in favour of H(0) or H(1), thus conserving valuable resources for future testing. A sequentially designed study can be more economical and less arbitrary than a study that makes use of conditional power or conditional coverage probability calculations to decide early stopping.

Aged↗

PubMed1996

Automatic embolus detection compared with human experts. A Doppler ultrasound study.

BACKGROUND AND PURPOSE: Transcranial Doppler ultrasound (TCD) reliably detects the occurrence of microembolic signals (MES). Unfortunately, TCD monitoring is a time-consuming and mentally strenuous procedure. The purpose of this study was to assess whether automatic embolus detection software devices acting as a "stand-alone system" are able to identify MES in patients with solid cerebral microemboli. METHODS: Ten records of TCD monitoring of the middle cerebral artery in patients with symptomatic high-grade carotid artery stenosis were analyzed for the moments at which MES occurred by four observers and three automatic detection software devices (RB11 on TC2000, Pioneer Version 2.10, and Embotec). The results of the three software systems were assessed on the basic assumption that MES were present if at least three of the four observers agreed. RESULTS: The average number of 1-second periods in which MES were detected by the four observers per tape ranged from 5 to 39. The overall kappa values (and SEs) for chance-corrected interobserver agreement between the four observers ranged from .94 (.02) to .99 (.01). The agreement between the software devices and the observers was lower, with kappa values (and SEs) ranging from .18 (.17) to .93 (.07). The RB11 and Embotec systems achieved a kappa value higher than 0.4 in all tapes. The Pioneer system failed to reach a kappa value of 0.4 in three tapes. The RB11 showed a sensitivity of 70% for detecting MES, the Embotec 62%, and the Pioneer 44%. CONCLUSIONS: In patients with symptomatic high-grade carotid artery stenosis, a high degree of agreement in the detection of moments of MES can be achieved between observers. The three automatic detection software devices reached less agreement. Supervision of TCD monitoring and assessment of MES by an experienced observer is still necessary.

Carotid Stenosis↗

PubMed1995

Factors that influence the provision of sexual health care by Dutch cancer nurses.

A descriptive-correlational design was used with a sample of Dutch cancer nurses (n = 104) to describe provision of sexual health care (SHC) and to explore influential factors. This report is limited to the second goal. The Theory of Reasoned Action provided the conceptual framework for investigation of five previously identified factors and one unexplored factor. Knowledge, comfort, attitude (towards sexuality) and subjective norm were significantly related with provision of SHC. Multiple regression analysis demonstrated that knowledge and comfort were significant explanatory variables, accounting for 37% of the variance.

Adult↗

PubMed1994

Impaired healing of cervical oesophagogastrostomies can be predicted by estimation of gastric serosal blood perfusion by laser Doppler flowmetry.

OBJECTIVE: To assess the value of relative blood perfusion of the gastric tube in prediction of impaired healing of cervical oesophagogastrostomies. DESIGN: Prospective study. SETTING: University hospital, The Netherlands. SUBJECTS: Thirty patients undergoing transhiatal oesophagectomy and partial gastrectomy for cancer of the oesophagus or oesophagogastric junction, with gastric tube reconstruction and cervical oesophagogastrostomy. MAIN OUTCOME MEASURES: Operative measurement of gastric blood perfusion at four sites by laser Doppler flowmetry and perfusion of the same sites after construction of the gastric tube expressed as a percentage of preconstruction values. RESULTS: The relative perfusion at the most proximal site of the gastric tube was significantly lower than at the more distal sites (p = 0.001). Nine of 18 patients (50%) in whom the perfusion of the proximal gastric tube was less than 70% of preconstruction values developed an anastomotic stricture, compared with only 1 of 12 patients (8%) with a relative perfusion of 70% or more (p = 0.024). A reduction in perfusion of the gastric tube did not predict leakage. CONCLUSION: Impaired anastomotic healing is unlikely if relative perfusion is 70% or more of preconstruction values. Perfusion of less than 70% partly predicts the occurrence of anastomotic stricture, but leakage cannot be predicted. Factors other than blood perfusion may have a role in the process of anastomotic healing.

Adult↗

PubMed1988

Positive tip cultures and related risk factors associated with intravascular catheterization in pediatric cardiac patients.

The incidence and risk factors of positive catheter tip cultures were studied prospectively in 392 consecutive children undergoing cardiac surgery under cover of cephalothin prophylaxis. A total of 1649 catheter tips were cultured and 58 (3.5%) yielded positive cultures. Specifically, the incidence of positive catheter tip cultures for iv, central venous, arterial and pulmonary arterial (PA) catheters was 0.9%, 5.9%, 3.9% and 10.6%, respectively, whereas one of the six surgically placed venous and arterial catheters had a positive tip culture and none of the 279 transthoracic catheters. Staphylococcus epidermidis was isolated from 79% of the positive tip cultures. Ten percent of the children had one or more positive tip cultures but none developed catheter-related septicemia or endocarditis. Stepwise logistic regression analysis revealed that longer in situ time (p less than .001), younger age (p less than .001), and inotropic support (p = .003) were significant independent predictors of risk for children developing positive catheter tip cultures. The safe in situ period for arterial, central venous, and PA catheters is 3 days in infants under 1 yr and 4 and 6 days for arterial and central venous catheters, respectively, in older children, if 0.95 cumulative probability of remaining free of a positive tip culture is accepted. The data generally support the bacteriologic safety of invasive hemodynamic monitoring in infants and children undergoing cardiac surgery.

Adolescent↗