Conditional and Unconditional Tests (and Sample Size) Based on Multiple Comparisons for Stratified 2 × 2 Tables.

The Mantel-Haenszel test is the most frequent asymptotic test used for analyzing stratified 2 × 2 tables. Its exact alternative is the test of Birch, which has recently been reconsidered by Jung. Both tests have a conditional origin: Pearson's chi-squared test and Fisher's exact test, respectively. But both tests have the same drawback that the result of global test (the stratified test) may not be compatible with the result of individual tests (the test for each stratum). In this paper, we propose to carry out the global test using a multiple comparisons method (MC method) which does not have this disadvantage. By refining the method (MCB method) an alternative to the Mantel-Haenszel and Birch tests may be obtained. The new MC and MCB methods have the advantage that they may be applied from an unconditional view, a methodology which until now has not been applied to this problem. We also propose some sample size calculation methods.

Tissue factor expressed by microparticles is associated with mortality but not with thrombosis in cancer patients.

A prothrombotic state is one of the hallmarks of malignancy and a major contributor to morbidity and mortality in cancer patients.Tissue factor (TF) is often overexpressed in malignancy and is a prime candidate in predicting the hypercoagulable state. Moreover, increased number of TF-exposing microparticles (MPs) in cancer patients may contribute to venous thromboembolism (VTE). We have conducted a prospective cohort study to determine whether elevated TF antigen, TF activity and TF associated to MPs (MPs-TF) are predictive of VTE and mortality in cancer patients. The studied population consisted of 252 cancer patients and 36 healthy controls. TF antigen and activity and MPs-TF were determined by ELISA and chromogenic assays. During a median follow-up of 10 months, 40 thrombotic events were recorded in 34 patients (13.5%), and 73 patients (28.9%) died. TF antigen and activity were significantly higher in patients than in controls (p<0.01) mainly in patients with advanced stages, whereas no differences were observed for TF activity of isolated MPs. We did not find a statistically significant association of TF variables with the risk of VTE. Multivariate analysis adjusting for age, sex, type of cancer and other confounding variables showed that TF activity (p<0.01) and MPs-TF activity (p<0.05) were independently associated with mortality. In conclusion, while TF variables were not associated with future VTE in cancer patients, we found a strong association of TF and MPs-TF activity with mortality, thus suggesting they might be good prognostic markers in cancer patients.

Inferences about a linear combination of proportions.

Statistical methods for carrying out asymptotic inferences (tests or confidence intervals) relative to one or two independent binomial proportions are very frequent. However, inferences about a linear combination of K independent proportions L = Σß(i)p(i) (in which the first two are special cases) have had very little attention paid to them (focused exclusively on the classic Wald method). In this article the authors approach the problem from the more efficient viewpoint of the score method, which can be solved using a free programme, which is available from the webpage quoted in the article. In addition the article offers approximate formulas that are easy to calculate, gives a general proof of Agresti's heuristic method (consisting of adding a certain number of successes and failures to the original results before applying Wald's method) and, finally, it proves that the score method (which verifies the desirable properties of spatial and parametric convexity) is the best option in comparison with other methods.

Solar urticaria enhanced through clothing.

Solar urticaria is characterized by itching, erythema and wheeling immediately after exposure to radiation in the ultraviolet (UVB, UVA) and visible spectra. Although its exact mechanism remains unknown, evidence supports an immunologic pathogenesis. We describe an unusual patient with solar urticaria who had more severe involvement in skin irradiated with UVA light through white clothing. We propose that optical whiteners in clothing and detergents had absorbed UVA radiation, transforming it into visible light, which was responsible for the urticarial response.