Marginal association measures for clustered data

The use of correlation coefficients in measuring the association between two continuous variables is common, but regular methods of calculating correlations have not been extended to the clustered data framework. For clustered data in which observations within a cluster may be correlated, regular inferential procedures for calculating marginal association between two variables can be biased. This is particularly true for data in which the number of observations in a given cluster is informative for the association being measured. In this paper, we apply the principle of inverse cluster size reweighting to develop estimators of marginal correlation that remain valid in the clustered data framework when cluster size is informative for the correlation being measured. These correlations are derived as analogs to regular correlation estimators for continuous, independent data, namely, Pearson's ρ and Kendall's τ. We present the results of a simple simulation study demonstrating the appropriateness of our proposed estimators and the inherent bias of other inferential procedures for clustered data. We illustrate their use through an application to data from patients with incomplete spinal cord injury in the U.S.A.     

Thorium-induced oxidative stress mediated toxicity in mice and its abrogation by diethylenetriamine pentaacetate

PURPOSE: Thorium ((232)Th, IV) preferentially accumulates in the liver, femur and spleen, which necessitates evaluation of its toxic effect in these organs. The present study was aimed at evaluation of liver function, oxidative stress and histological alterations in these organs. MATERIALS AND METHOds: Swiss albino mice were administered either with Thorium nitrate (10 mg/kg body weight/day equivalent to 1,090 pCi/kg body weight/day) for 30 days (1/40th dose of LD(50/30); the dose of thorium required to kill 50% of the test cohort within 30 days) intraperitoneally or with calcium salt of diethylenetriamine pentaacetate (Ca-DTPA, 100 micromole/kg body/weight) intravenously or both. Liver function tests and oxidative damage was assessed. The concentration of Th in the tissues was determined by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) method. RESULTS: Administration of Th prevented the increase in the body and liver weight and altered liver functions. Th treatment to mice showed a decrease in the activities and gene expression of antioxidant enzymes, and increased lipid peroxidation and protein carbonylation. The extent of observed oxidative damage was correlated with accumulation of Th in examined organs and further associated with histological alterations. Furthermore it was found that these effects were significantly lower when the chelating agent, Ca-DTPA, was given 1 h after Th injection. CONCLUSION: Administration of subtoxic concentration of Th to mice markedly altered the liver functions and induced oxidative stress in the liver, femur and spleen of mice. The results further demonstrated that Ca-DTPA significantly protected mice against the toxic effects of Th.     

Effect of raloxifene on the risk of new vertebral fracture in postmenopausal women with osteopenia or osteoporosis: a reanalysis of the Multiple Outcomes of Raloxifene Evaluation trial

Raloxifene reduces vertebral fracture risk in postmenopausal women with osteoporosis and established osteoporosis, but its efficacy in women with osteopenia has not been studied. The objective of this study was to evaluate the effect of raloxifene hydrochloride on the risk of vertebral fractures in postmenopausal women with osteopenia and to compare this effect with that in women with osteoporosis as defined by the bone mineral density (BMD) T-score at the hip. We studied the 3204 postmenopausal women with osteopenia or osteoporosis without vertebral fractures at baseline in the Multiple Outcomes of Raloxifene Evaluation trial. Compared with placebo, 60 mg/day raloxifene reduced the risk of new vertebral fractures at 3 years independent of baseline total hip BMD. The relative risk for new vertebral fractures for the raloxifene group compared with placebo was 0.53 (95% CI, 0.32-0.88) for those with osteopenia and 0.31 (0.06-0.71) for those with osteoporosis. In raloxifene-treated women the rate of vertebral fracture was similar in women with osteoporosis (2%) to that in women with osteopenia (1.9%). For clinically apparent vertebral fractures, the relative risk of fracture in the osteopenia group for raloxifene was 0.25 (0.04-0.63) compared with placebo. There were no new clinical vertebral fractures in women with osteoporosis receiving raloxifene, whereas four occurred in the placebo group. We conclude that treatment with 60 mg/day raloxifene significantly decreases the risk of new vertebral fractures and new clinical vertebral fractures in postmenopausal women without baseline vertebral fracture who have osteopenia or osteoporosis.     

Outcome of humeral shaft fractures treated by functional cast brace

Background:Functional brace application for isolated humeral shaft fracture persistently yields good results. Nonunion though uncommon involves usually the proximal third shaft fractures. Instead of polyethylene bivalve functional brace four plaster sleeves wrapped and molded with little more proximal extension expected to prevent nonunion of proximal third fractures. Periodic compressibility of the cast is likely to yield a better result. This can be applied on the 1^st day of the presentation as an outpatient basis. Comprehensive objective scoring system befitting for fracture humeral shaft is a need.Results:The results were assessed using 100 point scoring system where union allotted 30 points and 60 points allotted for angulations (10), elbow motion (10), shoulder abduction (10), shortening (5), rotation (5), absence of infection (10), absence of nerve palsy during treatment (10). Remaining 10 points were allotted for five items with two points each. They were the absence of skin sore, absence of vascular problem, absence of reflex sympathetic dystrophy (RSD), recovery of paralyzed nerve during injury and recovery of paralyzed nerve during treatment. Results were considered excellent with 90 and above, good with 80–89, fair with 70–79 and poor below 70 point. Results at 6 months were excellent in 43.94% (n = 29), good in 42.42% (n = 28), fair in 9.1% (n = 6), poor in 4.55% (n = 3). Union took place in 98.48% (n = 65) with an average of 10.3 weeks (range 6–16 weeks). 87.5% (n = 7) paralyzed radial nerve recovered. All wounds healed. Four patients had transient skin problem. One patient with mid shaft fracture had nonunion due to the muscle interposition.Conclusion:Modified functional cast brace is one of the options in treatment for humeral shaft fractures as it can be applied on the 1^st day of the presentation in most of the situations. Simple objective scoring system was useful particularly in uneducated patients.