Re-evaluating a vision-related quality of life questionnaire with item response theory (IRT) and differential item functioning (DIF) analyses

Background: For the Low Vision Quality Of Life questionnaire (LVQOL) it is unknown whether the psychometric properties are satisfactory when an item response theory (IRT) perspective is considered. This study evaluates some essential psychometric properties of the LVQOL questionnaire in an IRT model, and investigates differential item functioning (DIF). Methods: Cross-sectional data were used from an observational study among visually-impaired patients (n = 296). Calibration was performed for every dimension of the LVQOL in the graded response model. Item goodness-of-fit was assessed with the S-X2-test. DIF was assessed on relevant background variables (i.e. age, gender, visual acuity, eye condition, rehabilitation type and administration type) with likelihood-ratio tests for DIF. The magnitude of DIF was interpreted by assessing the largest difference in expected scores between subgroups. Measurement precision was assessed by presenting test information curves; reliability with the index of subject separation. Results: All items of the LVQOL dimensions fitted the model. There was significant DIF on several items. For two items the maximum difference between expected scores exceeded one point, and DIF was found on multiple relevant background variables. Item 1 ‘Vision in general’ from the “Adjustment” dimension and item 24 ‘Using tools’ from the “Reading and fine work” dimension were removed. Test information was highest for the “Reading and fine work” dimension. Indices for subject separation ranged from 0.83 to 0.94. Conclusions: The items of the LVQOL showed satisfactory item fit to the graded response model; however, two items were removed because of DIF. The adapted LVQOL with 21 items is DIF-free and therefore seems highly appropriate for use in heterogeneous populations of visually impaired patients. (aut.ref.

CD31+ T Cells Represent a Functionally Distinct Vascular T Cell Phenotype

In contrast to CD3(+)/CD31(-) cells, CD3(+)/CD31(+) cells aid in endothelial repair and revascularization. There are limited data regarding the functional differences between circulating CD3(+)/CD31(+) and CD3(+)/CD31(-) cells that may contribute to their divergent cardiovascular effects. The aim of the present study was to characterize functional differences between CD3(+)/CD31(+) and CD3(+)/CD31(-) cells. To address this aim, migratory capacity, proangiogenic cytokine release and apoptotic susceptibility of CD3(+)/CD31(+) and CD3(+)/CD31(-) cells were determined. Human CD3(+)/CD31(+) and CD3(+)/CD31(-)cells from peripheral blood were isolated using magnetic-activated cell sorting. CD3(+)/CD31(+) cells demonstrated significantly higher ( approximately 60%) migratory capacity to the chemokines SDF-1alpha (655+/-99 vs. 273+/-54 AU) and VEGF (618+/-99 vs. 259+/-57 AU) vs. CD3(+)/CD31(-) cells. Release of angiogenic cytokines G-CSF, interleukin-8 and matrix metallopeptidase-9 were all approximately 100% higher (P\u3c0.05) in CD3(+)/CD31(+) than CD3(+)/CD31(-) cells. CD3(+)/CD31(+) cells exhibited significantly higher intracellular concentrations of active caspase-3 (2.61+/-0.60 vs. 0.34+/-0.09 ng/mL) and cytochrome-c (21.8+/-1.4 vs. 13.7+/-1.0 ng/mL). In summary, CD3(+)/CD31(+) cells have greater migratory and angiogenic cytokine release capacity, but are more susceptible to apoptosis compared with CD3(+)/CD31(-) cells. Enhanced migratory capacity and angiogenic cytokine release may contribute to the vasculogenic properties of this unique T cell subpopulation

Virus validation of pH 4-treated human immunoglobulin products produced by the Cohn fractionation process

To assess the virus reducing capacity of Cohn's cold ethanol fractionation process for the production of intravenous (IVIg) and intramuscular (IMIg) immunoglobulin products, and treatment of these products at pH 4, a validation study of virus removal and/or inactivation was performed using both lipid-enveloped viruses [human immunodeficiency virus (HIV), bovine viral diarrhoea virus (BVDV) and pseudorabies virus (PSR)], and non-lipid-enveloped viruses [(simian virus 40 (SV40) and encephalomyocarditis virus (EMC)]. For the cold ethanol fractionation process, overall reduction factors of 3.0 logs, > or = 2.6 ( or = 2.6 ( or = 8.4 logs, > or = 4.0 logs, > or = 7.1 logs, 4.8 logs and 1.4 logs for HIV, BVDV, PSR, SV40 and EMC, respectively. The effectiveness of this process step could be enhanced by extending incubation to 40 h at pH 4.25 compared to 16 h at pH 4.05. The extended incubation, as applied in the production of IMIg, yields a reduction of infectivity of SV40 by > or = 5.5 ( or = 4.1 ( <7.1) logs. Storage of IMIg, which is formulated as a solution, at 2-8 degrees C also contributes to virus safety. For storage periods of 8 weeks or longer, reduction factors of 2 to 6 logs were found for all viruses, except for BVDV which remained unaffected. These data indicate that the production processes for IVIg and IMIg as described here have sufficient virus reducing capacity to achieve a high margin of virus safet

Childhood Bladder and Bowel Dysfunction Questionnaire: Development, Feasibility, and Aspects of Validity and Reliability

Objectives: The aim of the study was to develop a questionnaire evaluating the frequency of symptoms over time of concomitant childhood bladder and bowel dysfunctions (CBBDs) in 5- to 12-year-old children and to assess its feasibility and aspects of validity and reliability. Methods: The Childhood Bladder and Bowel Dysfunction Questionnaire (CBBDQ) was developed in phases according to COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) in cooperation with epidemiologists, pediatricians, physiotherapists (phases 1 and 5), and professional translators (phase 5): selection of items (Delphi-method), content validity (pilot), feasibility (interviews), structural validity and internal consistency (field testing), and guideline-based translation (Dutch-English). Participants were parents of children, ages 5 to 12 years (phases 2-4). Results: Parents of 1333 children (mean age 7.8 years [standard deviation 2.1]) were included. Most common were urinary incontinence (35.9%), enuresis (29.7%), and constipation/fecal incontinence (30.1%). Concomitant CBBD was seen in 74.2% of 1229 children. Originally, a 27-item CBBDQ was developed. After the pilot (48 parents) a 23-item version remained for evaluation of feasibility aspects by interviewing 56 parents. Based on 1229 completed questionnaires during field testing, the CBBDQ reduced to 18 items. Cronbach a values were 0.74 and 0.71 for bladder and bowel subscales, respectively. Feasibility and aspects of validity and reliability were satisfactory. A definitive and accepted English version of the CBBDQ is available. Conclusions: When completed by parents, the 18-item evaluative CBBDQ appears feasible, content, and structurally valid with good internal consistency for the bladder and bowel subscales. The Dutch and English versions will be introduced clinically and subjected to further psychometric evaluatio