Multiple imputation to deal with missing clinical data in rheumatologic surveys: an application in the WHO-ILAR COPCORD study in Iran

The aim of the article is demonstrating an application of multiple imputation [MI] for handling missing clinical data in the setting of rheumatologic surveys using data derived from 10291 people participating in the first phase of the Community Oriented Program for Control of Rheumatic Disorders [COPCORD] in Iran. Five data subsets were produced from the original data set. Certain demographics were selected as complete variables. In each subset, we created a univariate pattern of missingness for knee osteoarthritis status as the outcome variable [disease] using different mechanisms and percentages. The crude disease proportion and its standard error were estimated sgscrately for each complete data set to be used as true [baseline] values for percent bias calculation. The parameters of interest were also estimated for each incomplete data subset using two approaches to deal with missing data including complete case analysis [CCA] and MI with various imputation numbers. The two approaches were compared using appropriate analysis of variance. With CCA, percent bias associated with missing data was 8.67 [95% CI: 7.81-9.53] for the proportion and 13.67 [95% CI: 12.60-14.74] for the standard error. However, they were 6.42 [95% CI: 5.56-7.29] and 10.04 [95% CI: 8.97-11.11], respectively using the MI method [M=15]. Percent bias in estimating disease proportion and its standard error was significantly lower in missing data analysis using MI compared with CCA [P< 0.05]. To estimate the prevalence of rheumatic disorders such as knee osteoarthritis, applying MI using available demographics is superior to CCA

How much improvement is expected in ocular lesions of Behcet's disease treated with pulse cyclophospamide?

The natural history of ocular lesions in Behcet's disease is toward severe loss of vision/blindness in few years, whereas cytotoxic drugs have changed the outcome. Several open labeled cohort studies showed pulse cyclophosphamide [PCP] to be the best choice. Since one third of these patients are resistant to PCP it is important to know how much improve ment one can expect from the responders. To address this question, we selected patients who improved or maintained their baseline visual acuity after treatment. From a cohort of 528 patients [1056 eyes], 753 eyes were selected. At the beginning of the study PCP was given for one month as 0.75 to 1 g in perfusion, and then followed every 2 to 3 months. Prednisolone was also given as 0.5 mg/kg/daily and then tapered upon controlling inflammation. The mean +/- SD number of pulses was 11.5 +/- 8.5/month with follow-up of 20.6 +/- 19.8 months. Different disease activity indices such as visual acuity, posterior uveitis, retinal vasculitis, total inflammatory activity index [TIAI], total adjusted disease activity index [TADAI] were calculated at baseline and at last evaluation. The mean visual acuity improved from 2.4 to 4.4. The mean indices for posterior uveitis, retinal vasculitis, TIAI and TADAI improved from 2.2 to 1, 2.7 to 1.4, 19.3 to 9, and 27.2 to 20.5 respectively. The P value was less than 0.001 for all comparisons. Pulse cyclophosphamide is able to improve ocular lesions of Behcet's disease; therefore it may be used as a first choice, especially in retinal vasculitis

Levels of soluble IL-2 receptors in sera of Iranian patients with Behcet's disease

It has been shown that activated T-cells produce and release both IL-2 and IL 2 receptors [IL-2R]. The rate of IL-2 release is proportional to its cell surface expression and state of cell activation. To clarify the molecular basis of this immunological aberration, we analysed the amount of soluble IL-2R[SIL2-R] by an ELISA technique in 68 patients with Behcet's disease [BD], 28 patient controls [PC] and 31 normal controls [NC]. The data suggest that the amount of SIL-2R in BD is significantly higher [P<0.005] than that of NC. The same differences were seen between PC and NC[P<0.005]. However the level of SIL-2R in BD and PC were similar. This study suggests that inhibition of an immunoregulatory cytokine by its soluble receptors might occur in Vivo, as the reduction of SIL-2R levels approaching control values preceded clinical remission