Harriët Heijboer

Pediatric venous thromboembolic disease in one single center: congenital prothrombotic disorders and the clinical outcome

Summary.  To learn more about the frequencies of congenital prothrombotic disorders in pediatric venous thromboembolism (VTE) and the outcome of this disease, we evaluated consecutive patients from 0 to 18 years with objectively diagnosed VTE at a single tertiary center over a 12‐year period. We included 100 patients, with a median age at diagnosis of 1.0 year (range 2 days to 17 years). At least one underlying clinical condition was present in 96% of the patients. Factor (F)V G1691A mutation was present in 13%, FII G20210A mutation in 3%, antithrombin deficiency in 1%, protein C deficiency in 1% and protein S deficiency in 1% of the tested patients. Combined defects were present in 2.6% of the 77 patients with a complete work‐up. Positive family history appeared to be the only predictor for positive testing for congenital disorders (OR 14.9, 95% CI 1.9–113). The overall mortality rate was 20%. The cumulative recurrence‐free survival was 92% after 1 year of follow‐up, and 82% after 7 years. The incidence and severity of the post‐thrombotic syndrome was analyzed in a subgroup of 33 patients with VTE of the lower extremities. Twenty‐three (70%) patients developed PTS: moderate in three and mild in 20 patients. In conclusion, congenital prothrombotic disorders seem to play a role in the development of pediatric VTE, and the risk of complications of this disease is high.

Arterial spin labeling measurement of cerebral perfusion in children with sickle cell disease

To evaluate the applicability of arterial spin labeling (ASL) cerebral blood flow (CBF) measurements in children with sickle cell disease (SCD).

Neurocognitive deficits in children with sickle cell disease: a comprehensive profile†

Sickle cell disease (SCD) can lead to profound cerebral damage, associated with neurocognitive deficits. The aim of the current study was to evaluate a broad range of neurocognitive functions in children with SCD compared to a SES‐matched control group, in order to gain more insight into the specific deficits of these patients.

Neurocognitive deficits in children with sickle cell disease are associated with the severity of anemia

Although neurocognitive deficits in children with sickle cell disease (SCD) have been well documented, the etiology of these deficits has not been completely clarified. The aim of this study was to investigate the association of laboratory markers of disease severity and radiological parameters with neurocognitive functioning in children with SCD.

Behavioral and emotional problems in children with sickle cell disease and healthy siblings: Multiple informants, multiple measures

Behavioral and emotional problems in children with sickle cell disease (SCD) may be related to disease factors, or to socio‐demographic factors. The aim of this study was to investigate the prevalence of behavioral and emotional problems in children with SCD living in a Western European country, compared to healthy siblings (who were comparable in age, gender, ethnicity, and socio‐economic status—SES), and to a Dutch norm population.

Development and validation of a pediatric severity index for sickle cell patients

There is no instrument to measure severity of sickle cell disease (SCD) in pediatric patients that is generally accepted. The aim of this study was to develop and validate a severity index for SCD in children. We developed an index consisting of 12 items and tested its validity of the index using data from 92 children. We tested whether different scores were obtained for patients classified by severity both subjectively and objectively by a partially validated existing index. Furthermore, we tested whether the index could differentiate patients classified according to genotype or the number of α‐gene deletions and evaluated whether the score on the index was correlated with the average number and days of hospitalizations/year, age and a risk of death score. We explored the effect of three different weighting systems (Score A, B, and C) to summarize these items. All weightings demonstrated a significant difference between the scores of mild, moderate, and severely affected patients, as classified by a subjective rating or with an existing index (P < 0.01). The index clearly differentiated patients by genotype (P < 0.01) or α‐gene deletions (P < 0.01). The correlation with hospitalization was moderate. Age and the risk of death score were weakly associated with the pediatric severity index for SCD. This is the first pediatric SCD severity index that was developed and validated using modern clinimetric methodology. The validity and reliability of this index should be further evaluated in a prospective study including a larger cohort, preferably diagnosed at birth. Am. J. Hematol., 2010.

Mortality and causes of death in children with sickle cell disease in the Netherlands, before the introduction of neonatal screening

This study analyzed the mortality and causes of death in sickle cell disease patients in the Netherlands, to provide a baseline for monitoring the effect of the recently introduced neonatal screening programme and to indicate areas of improvement in the care for these patients. All children (<18 years) diagnosed with sickle cell disease in a tertiary hospital from 1985 to 2007 were included. Vital status was determined up to March 2008. A total of 298 children were included: 189 (63%) patients had HbSS, 17 (6%) HbSβ0 thalassaemia, 72 (24%) HbSC and 20 (7%) HbSβ+ thalassaemia. Twelve patients (4%) died during a total follow‐up of 3896 patient years. All known deaths were sickle cell disease‐related. Meningitis/sepsis (n = 4; 33%), stroke (n = 3; 25%) and death during a visit to the country of origin (n = 3; 25%) were the most common causes of death. The overall mortality rate was 0·27 deaths/100 patient years [95% confidence interval (CI): 0·15–0·43]. The estimated survival at the age of 18 years was 97·3% (95% CI: 95–99%). This report confirms that the burden of mortality in sickle cell disease is increasingly shifting to adults. It is recommended that compliance to antibiotic prophylaxis, thorough counselling and support for patients travelling abroad and specialized peri‐operative care should receive continuous attention.

Early occurrence of red blood cell alloimmunization in patients with sickle cell disease

Red blood cell (RBC) alloimmunization is a major complication of transfusion therapy in sickle cell disease (SCD). Identification of high‐risk patients is hampered by lack of studies that take the cumulative transfusion exposure into account. In this retrospective cohort study among previously non‐transfused SCD patients in the Netherlands, we aimed to elucidate the association between the cumulative transfusion exposure, first alloimmunization and independent risk factors. A total of 245 patients received 11 952 RBC units. Alloimmunization occurred in 43 patients (18%), half of them formed their first alloantibody before the 8th unit. In patients with exposure to non‐extended matched transfusions (ABO and RhD) the cumulative alloimmunization risk increased up to 35% after 60 transfused units. This was significantly higher compared to a general transfused population (HR 6.6, CI 4.2–10.6). Receiving the first transfusion after the age of 5 was an independent risk factor for alloimmunization (HR 2.3, CI 1.0–5.1). Incidental, episodic transfusions in comparison to chronic scheme transfusions (HR 2.3, CI 0.9–6.0), and exposure to non‐extended matched units in comparison to extended matching (HR 2.0, CI 0.9–4.6) seemed to confer a higher alloimmunization risk. The majority of first alloantibodies are formed after minor transfusion exposure, substantiating suggestions of a responder phenotype in SCD and stressing the need for risk factor identification. In this study, older age at first transfusion, episodic transfusions and non‐extended matched transfusions appeared to be risk factors for alloimmunization. Am. J. Hematol. 91:763–769, 2016.

Double disadvantage: A case control study on health-related quality of life in children with sickle cell disease.

BackgroundLow health-related quality of life (HRQoL) of children with sickle cell disease (SCD) may be associated with consequences of the disease, or with the low socio-economic status (SES) of this patient population. The aim of this study was to investigate the HRQoL of children with SCD, controlling for SES by comparing them to healthy siblings (matched for age and gender), and to a Dutch norm population.MethodsThe HRQoL of 40 children with homozygous SCD and 36 healthy siblings was evaluated by the KIDSCREEN-52. This self-report questionnaire assesses ten domains of HRQoL. Differences between children with SCD and healthy siblings were analyzed using linear mixed models. One-sample t-tests were used to analyze differences with the Dutch norm population. Furthermore, the proportion of children with SCD with impaired HRQoL was evaluated.ResultsIn general, the HRQoL of children with SCD appeared comparable to the HRQoL of healthy siblings, while children with SCD had worse HRQoL than the Dutch norm population on five domains (Physical Well-being, Moods & Emotions, Autonomy, Parent Relation, and Financial Resources). Healthy siblings had worse HRQoL than the Dutch norm population on three domains (Moods & Emotions, Parent Relation, and Financial Resources). More than one in three children with SCD and healthy siblings had impaired HRQoL on several domains.ConclusionThese findings imply that reduced HRQoL in children with SCD is mainly related to the low SES of this patient population, with the exception of disease specific effects on the physical and autonomy domain. We conclude that children with SCD are especially vulnerable compared to other patient populations, and have special health care needs.

Risk factor analysis of cerebral white matter hyperintensities in children with sickle cell disease

Sickle cell disease (SCD) is complicated by silent cerebral infarcts, visible as white matter hyperintensities (WMHs) on magnetic resonance imaging (MRI). Both local vaso‐occlusion, elicited by endothelial dysfunction, and insufficiency of cerebral blood flow (CBF) have been proposed to be involved in the aetiology. We performed an explorative study to investigate the associations between WMHs and markers of endothelial dysfunction and CBF by quantifying WMH volume on 3·0 Tesla MRI. We included 40 children with HbSS or HbSβ0thalassaemia, with a mean age of 12·1 ± 2·6 years. Boys demonstrated an increased risk for WMHs (odds ratio 4·5, 95% confidence interval 1·2–17·4), unrelated to glucose‐6‐phosphate dehydrogenase deficiency. In patients with WMHs, lower fetal haemoglobin (HbF) was associated with a larger WMH volume (regression coefficient = −0·62, R2 = 0·25, P = 0·04). Lower ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) levels were associated with lower CBF in the white matter (regression coefficient = 0·07, R2 = 0·15, P = 0·03), suggesting that endothelial dysfunction could potentially hamper CBF. The findings of our explorative study suggest that a high level of HbF may be protective for WMHs and that endothelial dysfunction may contribute to the development of WMHs by reducing CBF.