Estimation of linear models with inequality restrictions

Statistical Methods

Een vooruitziende blik

Ontwikkelen en toepassen van statistische modellen ten behoeve van medisch weten schappelijk onderzoe

Inhaled corticosteroids and growth of airway function in asthmatic children

Airway inflammation and remodelling play an important role in the pathophysiology of asthma. Remodelling may affect childhood lung function, and this process may be reversed by anti-inflammatory treatment. The current study assessed longitudinally whether asthma affects growth of airway function relative to airspaces, and if so whether this is redressed by inhaled corticosteroids (ICS). Every 4 months for up to 3 yrs, lung function was assessed in 54 asthmatic children (initial age 7-16 yrs), who inhaled 0.2 mg salbutamol t.i.d. and 0.2 mg budesonide t.i.d. (beta2-agonist (BA)+ICS), or placebo (PL) t.i.d. (BA+PL) in a randomised, double-blind design. Measurements were carried out before and after maximal bronchodilation. Airway growth was assessed from the change of forced expiratory volume in one second and of maximal expiratory flows (at 60% and 40% of total lung capacity (TLC) remaining in the lung) relative to TLC, as measures of more central, intermediate and more peripheral airways. Growth patterns were compared with the longitudinal findings in 376 healthy children. Airway patency after maximal bronchodilation in patients on BA+PL remained reduced compared to healthy subjects, whereas in patients on BA+ICS a marked improvement was observed to subnormal. No differences between patients and controls could be demonstrated for growth patterns of central and intermediate airway function. Compliance with BA+ICS was 75% of the prescribed dose, resulting in significant, sustained improvement of symptoms and postbronchodilator calibre of central and intermediate airways to subnormal within 2 months, but postbronchodilator small airway patency remained reduced, though improved compared to patients on BA+PL. Anti-inflammatory treatment of asthmatic children is associated with normal functional development of central and intermediate airways. The persistently reduced postbronchodilator patency of peripheral airways may reflect remodelling, or insufficient anti-inflammatory treatment

"Month related variability in immunological test results; implications for immunological follow-up studies."

This longitudinal study was originally designed to detect changes in the in vitro immune response of healthy subjects as a result of a psychological intervention. In this study a significant proportion, about 70%, of the immunological variability in the test results was accounted for by the differences in immunological response levels of the subjects. Apart from this between-subject-effect, a significant proportion of the variability in test results was related to the month of data sampling. The month-effect was computed in such a way that the between-subject variation was taken into account. This resulted in a more accurate estimation of the month-effect. Even after correction for the intervention, i.e. the defence of the PhD thesis, the effect of month of data sampling remains significant for mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, percentage of CD4 and CD8 cells, and for the response to the mitogens phytohaemagglutinin, pokeweed mitogen and concanavalin A as well as the results for the mixed lymphocyte culture for one pool out of three. In contrast, no significant month-effect was observed for the whole blood cell counts, for the differential white blood cell counts as determined by monoclonal antibody staining for cell surface markers CD3, CD16, TAC and OKM1, nor for the immunoglobulin IgM and IgG serum levels. Likewise the cell-mediated lympholysis activities measured against three pools of stimulator cells remained unaltered. We discuss the implications for future immunological follow-up studies of the observation that a significant proportion of the variability in immunological test results is related to differences between subjects and to the month of data sampling

Anticoagulation with or without Clopidogrel after Transcatheter Aortic-Valve Implantation

BACKGROUND The roles of anticoagulation alone or with an antiplatelet agent after transcatheter aortic-valve implantation (TAVI) have not been well studied. METHODS We performed a randomized trial of clopidogrel in patients undergoing TAVI who were receiving oral anticoagulation for appropriat