Information on Center Characteristics as Costs' Determinants in Multicenter Clinical Trials: Is Modeling Center Effect Worth the Effort?

Objectives:  Several methodological problems arise when health outcomes and resource utilization are collected at different sites. To avoid misleading conclusions in multi-center economic evaluations the center effect needs to be taken into adequate consideration. The aim of this article is to compare several models, which make use of a different amount of information about the enrolling center.
Methods:  To model the association of total medical costs with the levels of two sets of covariates, one at patient and one at center level, we considered four statistical models, based on the Gamma model in the class of the Generalized Linear Models with a log link, which use different amount of information on the enrolling centers. Models were applied to Cost of Strategies after Myocardial Infarction data, an international randomized trial on costs of uncomplicated acute myocardial infarction (AMI).
Results:  The simple center effect adjustment based on a single random effect results in a more conservative estimation of the parameters as compared with approaches which make use of deeper information on the centers characteristics.
Conclusions:  This study shows, with reference to a real multicenter trial, that center information cannot be neglected and should be collected and inserted in the analysis, better in combination with one or more random effect, taking into account in this way also the heterogeneity among centers because of unobserved centers characteristics.     

Measurement of renin in segmental renal veins of hypertensives

In 27 of 270 patients studies for possible renovascular hypertension, a lesion affecting a segmental renal artery was seen on angiography. In 22 patients who had sufficient data, the significance of measuring segmental-renal-vein renin in the diagnosis and treatment of segmental disease was evaluated. In 11 (50%), the renin values of segmental vessels supported the clinical diagnosis. In four (36%) of these 11, a high-renin-release area would not have been identified without the stress of upright posture. Successful treatment of hypertension was achieved in six of nine patients who had a revascularization procedure or resection of the segmental vessels. Samples from involved and uninvolved segments of the kidney as well as from the contralateral renal vein and inferior vena cava, together with the stimuli of sodium and volume depletion augmented by upright posture, enabled confirmation of the angiographic diagnosis of segmental-renovascular hypertension.     

Absorption of iron from unmodified maize and genetically altered, low-phytate maize fortified with ferrous sulfate or sodium iron EDTA

BACKGROUND: Reducing the phytate content in grains by genetic manipulation is a novel approach to increasing nonheme-iron absorption from mixed diets. Fractional iron absorption from a genetically modified strain of low-phytate maize (LPM) increased significantly, by 50%. OBJECTIVE: We assessed iron absorption from porridges prepared from the same LPM (lpa-1-1 mutant) and unmodified wild-type maize (WTM), both of which were fortified with either ferrous sulfate or sodium iron EDTA. DESIGN: Porridges providing 3.4 mg Fe were fortified with either ferrous sulfate or sodium iron EDTA to provide an additional 1 mg Fe/serving. In 14 nonanemic women, iron absorption was measured as the amount of radioiron incorporated into red blood cells (extrinsic tag method) 12 d after consumption of the study diets. RESULTS: No significant effect of phytate content on iron absorption was found when porridge was fortified with either sodium iron EDTA or ferrous sulfate. Fractional absorption of iron from WTM porridge fortified with sodium iron EDTA (5.73%) was 3.39 times greater than that from the same porridge fortified with ferrous sulfate (1.69%). Fractional absorption of iron from the sodium iron EDTA-fortified LPM porridge (5.40%) was 2.82 times greater than that from LPM porridge fortified with ferrous sulfate (1.91%) (P<0.0001 for both comparisons, repeated-measures analysis of variance). Thus, the previously identified benefit of LPM was no longer detectable when maize porridge was fortified with additional iron. CONCLUSION: Iron was absorbed more efficiently when the fortificant was sodium iron EDTA rather than ferrous sulfate, regardless of the type of maize.