A.H.G.S. van der Ven

A Rasch analysis of Raven’s standard progressive matrices

Abstract Unidimensionality was investigated for Raven’s Standard Progressive Matrices, one of the most widely used intelligence tests in the world. The test was administered as part of a research project devoted to the identification of highly gifted children. Unidimensionality was tested by means of the Rasch model, which was applied to subsets A–E separately. The Rasch model was not rejected for sets A, C and D. It was rejected for sets B and E, meaning that the items of these sets measure at least two different dimensions. It was hypothesized that these dimensions are Gestalt continuation and analogical reasoning for set B, and analogical reasoning and coping for set E. In the case of set C Rasch homogeneity could be considerably improved by assuming a second factor, apart from analogical reasoning, which was identified as lack of resistance to perceptual distractors. Splitting of set B into appropriate subsets yielded two unidimensional subsets, B1 and B2. Splitting of set E yielded one unidimensional subset E1 and a heterogeneous, multidimensional subset E2. Set C was redefined by disregarding some of its items. At the level of the newly defined subset scores the factor analogical reasoning is common to all subsets. The factor Gestalt continuation is common to the subsets A and B1. However, the reliability of these subsets were very low, implying that this factor might be too weak to be distinguishable in a factor analysis. The factors coping and lack of resistance to perceptual distractors are both unique. Therefore, one might expect the emergence of only one factor when a factor analysis would be performed on all newly defined subsets. However, factor analysis of the newly defined subsets yielded two factors. Further inspection of the factor plot showed that the emergence of a second factor could be considered as an artefact due to the skewness of the subset scores.

Translating the role of vitamin D3 in infectious diseases

Vitamin D3 affects both the innate as well as adaptive immune responses. Epidemiological studies have established that vitamin D3 deficiency plays an important role in tuberculosis (TB) and viral influenza prevalence as well as susceptibility to active disease in TB. Vitamin D3 status has been associated with the clinical course of HIV infection and drug interaction with anti-retroviral therapy. This article reviews the immunomodulatory capacity of vitamin D3 and examines the impact of vitamin D3 supplementation as a preventive or therapeutic intervention with the intent to uncover its potential therapeutic application in infectious diseases and to identify novel areas for future research. We present a review of randomized, controlled clinical studies conducted in humans which included assessment of the immune function or clinical outcome as study end points. Current data support vitamin D3 supplementation as risk-modifying intervention in tuberculosis and viral respiratory tract infection, but the optimal dosage regimen remains to be determined. However, to date the knowledge on its role in fungal infection and sepsis is limited although a potential benefit could be harnessed from its ability to curtail the unrestrained pro-inflammatory response and therefore prevent excessive collateral tissue damage.

Scalability, reliability, and validity of the benzodiazepine dependence self-report questionnaire in outpatient benzodiazepine users

As there is no multidimensional instrument available that reflects the severity of benzodiazepine (BZD) dependence comprehensively, the Benzodiazepine Dependence Self-Report Questionnaire (Bendep-SRQ) was developed and investigated. The Bendep-SRQ, Symptom Checklist-90 (SCL-90), Schedules for Clinical Assessments in Neuropsychiatry (SCAN), and Addiction Severity Index-Revised (ASI-R) were administered to 115 general practice (GP) patients, 124 psychiatric outpatients, and 33 self-help patients who were using BZDs. Factor and Rasch analyses were applied to construct scales. Reliability assessments were made in terms of subject discriminability, item discriminability, and test-retest stability. To support the construct validity of the scales, theoretical rationales were required to explain the specific item order provided by the Rasch scale values. To assess the concurrent and discriminant validity, a matrix consisting of the above-mentioned measures was factor-analyzed. Four Rasch-homogeneous scales were delineated: problematic use, preoccupation, lack of compliance, and withdrawal. Nearly all subject discriminability, item discriminability, and test-retest results indicated good reliability. A BZD dependence factor was extracted with high loadings for the Bendep-SRQ scales and the concurrent measures. The discriminant measures had high loadings on other factors. The scalability, reliability, and validity of the Bendep-SRQ scales appeared to be good. The Bendep-SRQ shows great promise as a useful and easily manageable instrument for assessment of the severity of BZD dependence in clinical practice and scientific research.

Dynamics of nasopharyngeal bacterial colonisation in HIV-exposed young infants in Tanzania

To estimate the prevalence of nasopharyngeal bacterial colonisation (NPBC) patterns in young Tanzanian HIV‐exposed infants and to analyse the influence of maternal NPBC and of the infants HIV status on the NPBC pattern.

Study of viremic profile in febrile specimens of chikungunya in Bandung, Indonesia

BACKGROUND Data regarding the viremia profile of chikungunya virus (CHIKV) infected patients especially during the pre-febrile period is limited. OBJECTIVE To obtain virological kinetic data on CHIKV infections. STUDY DESIGN A two-week community observation for dengue transmission was conducted in Bandung, Indonesia, from 2005 to 2009. Acute specimens from non-dengue febrile patients were screened by pan-alphavirus conventional RT-PCR. The positives were confirmed for CHIKV RNA by a specific RT-PCR followed by sequencing. Simultaneously these specimens were also cultured in Vero cells and tested for anti-CHIK IgM MAC-ELISA. All the available serial specimens,including the pre-febrile specimens, from confirmed CHIK cases, were tested by virus isolation, RT-PCR, qRT-PCR, and CHIK IgM ELISA. RESULTS There were five laboratory confirmed CHIK cases identified and studied. Among these, viremia was determined to extend from as early as 6 days prior to until 13 days post fever onset. Quantitative RT-PCR showed viremia peaked at or near onset of illness. CONCLUSION In this study, individuals were identified with viremia prior to fever onset and extending beyond the febrile phase. This extended viremic phase has the potential to impact transmission dynamics and thus the public health response to CHIK outbreaks.

Inhibition in Prolonged Work Tasks.

A new model is presented that explains reaction time fluctuations in prolonged work tasks. The model extends the so-called Poisson-Erlang model and can account for long-term trend effects in the reaction time curve. The model is consistent with Spearmans hy pothesis that inhibition increases during work and de creases during rest. Predictions concerning the long- term trend were tested against data from the Bourdon- Vos cancellation test. The long-term trend in the mean and in the variance was perfectly described by the model. A goodness-of-fit test comparing frequency distributions of observed reaction and simulated reac tion times was also supported by the model. Index terms: concentration, continuous work, distraction, in hibition, prolonged work, reaction time, response time.

Human recombinant alkaline phosphatase inhibits ex vivo platelet activation in humans

Sepsis-associated acute kidney injury (AKI) is associated with high morbidity and mortality. Excessive platelet activation contributes to AKI through the formation of microthrombi and amplification of systemic inflammation. Two phase II trials demonstrated that bovine-intestinal alkaline phosphatase (AP) improved renal function in critically ill patients with sepsis-associated AKI. In this study, we characterised the platelet-inhibiting effects of a human recombinant AP. Whole blood and platelet-rich plasma (PRP) of healthy volunteers (n=6) was pre-treated ex vivo with recAP, whereafter platelet reactivity to ADP, collagen-related peptide (CRP-XL) and Pam3CSK4 was determined by flow cytometry. RecAP (40 U/ml) reduced the platelet reactivity to ADP (inhibition with a median of 47 %, interquartile range 43-49 %; p<0.001) and tended to reduce platelet reactivity to CRP-XL (9 %, 2-25 %; p=0.08) in whole blood. The platelet-inhibiting effects of recAP were more pronounced in PRP both for ADP- (64 %, 54-68 %; p=0.002) and CRP-XL-stimulated samples (60 %, 46-71 %; p=0.002). RecAP rapidly converted ADP into adenosine, whereas antagonism of the A2A adenosine receptor partially reversed the platelet inhibitory effects of recAP. Platelets of septic shock patients (n=5) showed a 31% (22-34%; p=0.03) more pronounced reactivity compared to healthy volunteers, and this was completely reversed by recAP treatment. In conclusion, we demonstrate that recAP inhibits ex vivo human platelet activation through dephosphorylation of ADP and formation of adenosine as its turnover product. RecAP is able to reverse the platelet hyperreactivity present in septic shock patients. These effects may contribute to the beneficial effects of recAP as a new therapeutic candidate for sepsis-associated AKI.

Antibiotic resistance of Streptococcus pneumoniae colonising the nasopharynx of HIV-exposed Tanzanian infants.

To determine antibiotic susceptibility of colonising pneumococcal serotypes in HIV‐exposed infants before the introduction of the 13‐valent pneumococcal conjugate vaccine (PCV13), because HIV‐exposed infants are at increased risk of invasive pneumococcal infections.

The knowledge or random guessing model for matching tests

The knowledge or random guessing (KRG) model was applied to matching tests. A matching test typically consists of two lists of alternatives. The response alternatives in the first list might consist of several terms to be defined, and the question alternatives in the second list would then consist of the definitions. Examinees are instructed to match the question alternatives to the response alternatives. According to the KRG model, if an examinee knows the correct answer, the correct answer will be chosen; however, if the examinee does not know the correct match, he/she will select the question alternative by guessing at random. Reliability formulas for the number of correct matchings based on the KRG model are given by Zimmerman and Williams (1982). Before applying these formulas, an appropriate statistical test should be used to test whether the model holds. A goodness-of-fit test is developed that is especially sensitive to the assumption of random guessing. Moreover, a simplified version of the model is presented in which the alternatives are ordered according to a Guttman scale. Three examples are given in which the model is applied to real data. It appears that in many cases examinees use coping strategies that violate the assumption of random guessing. A suggestion is made for the develop ment of a somewhat more complex model that takes into account examinee coping strategies and that can be considered an extension of the KRG model.

The Hardy distribution for golf hole scores

In an article entitled ‘A Mathematical Theorem about Golf’ [1] G.H. Hardy introduced a simple model of golfing. He assumed, that, at one hole, a golfer has probability p of gaining a stroke with a single shot, and probability q that his shot costs him a stroke. Such strokes will be described as good ( G ) or bad ( B ), respectively, leaving probability 1 − p − q for an ordinary ( O ) stroke (see also [2]). For example, on a par four hole, successive strokes OGO will result in a birdie (a score which is one stroke less than par) and BBGOO in a bogey (a score which is one stroke more than par). In this paper the probability distribution P(T k = n ) will be derived for the number of strokes T a player may take on a hole of par k .