Classic infantile Pompe patients approaching adulthood: a cohort study on consequences for the brain

AIM

To examine the long-term consequences of glycogen storage in the central nervous system (CNS) for classic infantile Pompe disease using enzyme replacement therapy.

METHOD

Using neuropsychological tests and brain magnetic resonance imaging (MRI), we prospectively assessed a cohort of 11 classic infantile Pompe patients aged up to 17 years.

RESULTS

From approximately age 2 years onwards, brain MRI showed involvement of the periventricular white matter and centrum semiovale. After 8 years of age, additional white-matter abnormalities occurred in the corpus callosum, internal and external capsule, and subcortical areas. From 11 years of age, white-matter abnormalities were also found in the brainstem. Although there seemed to be a characteristic pattern of involvement over time, there were considerable variations between patients, reflected by variations in neuropsychological development. Cognitive development ranged from stable and normal to declines that lead to intellectual disabilities.

INTERPRETATION

As treatment enables patients with classic infantile Pompe disease to reach adulthood, white-matter abnormalities are becoming increasingly evident, affecting the neuropsychological development. Therefore, we advise follow-up programs are expanded to capture CNS involvement in larger, international patient cohorts, to incorporate our findings in the counselling of parents before the start of treatment, and to include the brain as an additional target in the development of next-generation therapeutic strategies for classic infantile Pompe disease.

WHAT THIS PAPER ADDS

In our long-term survivors treated intravenously with enzyme replacement therapy, we found slowly progressive symmetric white-matter abnormalities. Cognitive development varied from stable and normal to declines towards intellectual disabilities.

Genotype-phenotype relationship in mucopolysaccharidosis II: predictive power of IDS variants for the neuronopathic phenotype

AIM

Mucopolysaccharidosis type II (MPS II) is caused by variants in the iduronate-2-sulphatase gene (IDS). Patients can be either neuronopathic with intellectual disability, or non-neuronopathic. Few studies have reported on the IDS genotype-phenotype relationship and on the molecular effects involved. We addressed this in a cohort study of Dutch patients with MPS II.

METHOD

Intellectual performance was assessed for school performance, behaviour, and intelligence. Urinary glycosaminoglycans were quantified by mass spectrometry. IDS variants were analysed in expression studies for enzymatic activity and processing by immunoblotting.

RESULTS

Six patients had a non-neuronopathic phenotype and 11 a neuronopathic phenotype, three of whom had epilepsy. Total deletion of IDS invariably resulted in the neuronopathic phenotype. Phenotypes of seven known IDS variants were consistent with the literature. Expression studies of nine variants were novel and showed impaired IDS enzymatic activity, aberrant intracellular processing, and elevated urinary excretion of heparan sulphate and dermatan sulphate irrespective of the MPS II phenotype.

INTERPRETATION

We speculate that very low or cell-type-specific IDS residual activity is sufficient to prevent the neuronal phenotype of MPS II. Whereas the molecular effects of IDS variants do not distinguish between MPS II phenotypes, the IDS genotype is a strong predictor.

A long term follow-up study of the development of hip disease in Mucopolysaccharidosis type VI

Hip problems in Mucopolysaccharidosis type VI (MPS VI) lead to severe disability. Lack of data on the course of hip disease in MPS VI make decisions regarding necessity, timing and type of surgical intervention difficult. We therefore studied the development of hip pathology in MPS VI patients over time. Data were collected as part of a prospective follow-up study. Standardized supine AP pelvis and frog leg lateral radiographs of both hips were performed yearly or every 2years. Image assessment was performed quantitatively (angle measurements) and qualitatively (hip morphology). Clinical burden of hip disease was evaluated by physical examination, six minute walking test (6MWT) and a questionnaire assessing pain, wheelchair-dependency and walking distance. A total of 157 pelvic radiographs of 14 ERT treated MPS VI patients were evaluated. Age at first image ranged from 2.0 to 21.1years. Median follow up duration was 6.8years. In all patients, even in the youngest, the acetabulum and os ilium were dysplastic. Coverage of the femoral head by the acetabulum improved over time, but remained insufficient. While the femoral head appeared normal in the radiographs at young age, the ossification pattern became abnormal in all patients over time. In all patients the distance covered in the 6MWT was reduced (median Z scores -3.3). Twelve patients had a waddling gait. Four patients were partially wheelchair-dependent and ten patients had limitations in their maximum walking distance. In conclusion, clinically significant hip abnormalities develop in all MPS VI patients from very early in life, starting with deformities of the os ilium and acetabulum. Femoral head abnormalities occur later, most likely due to altered mechanical forces in combination with epiphyseal abnormalities due to glycosaminoglycan storage. The final shape and angle of the femoral head differs significantly between individual MPS VI patients and is difficult to predict.

Effects of a higher dose of alglucosidase alfa on ventilator-free survival and motor outcome in classic infantile Pompe disease: an open-label single-center study

BACKGROUND

Though enzyme-replacement therapy (ERT) with alglucosidase alfa has significantly improved the prospects for patients with classic infantile Pompe disease, some 50 % of treated infants do not survive ventilator-free beyond the age of 3 years. We investigated whether higher and more frequent dosing of alglucosidase alfa improves outcome.

METHODS

Eight cross-reactive immunological material (CRIM) positive patients were included in the study. All had fully deleterious mutations in both GAA alleles. Four received a dose of 20 mg/kg every other week (eow) and four received 40 mg/kg/week. Survival, ventilator-free survival, left-ventricular mass index (LVMI), motor outcome, infusion-associated reactions (IARs), and antibody formation were evaluated.

RESULTS

All eight patients were alive at study end, seven of them remained ventilator-free. The patient who became ventilator dependent was treated with 20 mg/kg eow. Three of the four patients receiving 20 mg/kg eow learned to walk; two of them maintained this ability at study end. All four patients receiving 40 mg/kg/week acquired and maintained the ability to walk at study end (ages of 3.3-5.6 years), even though their baseline motor functioning was poorer. There were no apparent differences between the two dose groups with respect to the effect of ERT on LVMI, the number of IARs and antibody formation.

CONCLUSIONS

Our data may suggest that a dose of 40 mg/kg/week improves outcome of CRIM positive patients over that brought by the currently recommended dose of 20 mg/kg eow. Larger studies are needed to draw definite conclusions.

Quality of life and participation in daily life of adults with Pompe disease receiving enzyme replacement therapy: 10 years of international follow-up

BACKGROUND

Pompe disease is an inheritable metabolic disorder for which enzyme replacement therapy (ERT) has been available since 2006. Effects of ERT have been shown on distance walked, pulmonary function and survival. We investigated whether it also improves quality of life and participation in daily life in adult patients with the disease.

METHODS

In an international survey, we assessed quality of life (Short Form 36, SF-36) and participation (Rotterdam Handicap Scale, RHS) annually between 2002 and 2012. Repeated measurements mixed effects models were used to describe the data over time.

RESULTS

Responses were available for 174 adult patients. In the periods before and after start of ERT, the median follow-up times were 4 years each (range 0.5-8). The SF-36 Physical Component Summary measure (PCS) deteriorated before ERT (-0.73 score points per year (sp/y); CI 95 % -1.07 to -0.39), while it improved in the first 2 years of ERT (1.49 sp/y; CI 0.76 to 2.21), and remained stable thereafter. The Mental Component Summary measure (MCS) remained stable before and during ERT. After declining beforehand (-0.49 sp/year; CI -0.64 to-0.34), the RHS stabilized under ERT.

CONCLUSION

In adult patients with Pompe disease, ERT positively affects quality of life and participation in daily life. Our results reinforce previous findings regarding the effect of ERT on muscle strength, pulmonary function and survival.

Long-term cognitive follow-up in children treated for Maroteaux-Lamy syndrome

BACKGROUND

It remains unclear to what extent the brain is affected by Maroteaux-Lamy syndrome (MPS VI), a progressive lysosomal storage disorder. While enzyme replacement therapy (ERT) elicits positive effects, the drug cannot cross the blood-brain barrier. We therefore studied cognitive development and brain abnormalities in the Dutch MPS VI patient population treated with ERT.

METHODS

In a series of 11 children with MPS VI (age 2 to 20 years), we assessed cognitive functioning and brain magnetic resonance imaging prospectively at the start of ERT and at regular times thereafter up to 4.8 years. We also assessed the children's clinical characteristics, their siblings' cognitive development, and their parents' educational levels.

RESULTS

The patients' intelligence scores ranged from normal to mentally delayed (range test scores 52-131). In 90%, their scores remained fairly stable during follow-up, generally lying in the same range as their siblings' test scores (median for patients = 104, median for siblings = 88) and comparing well with the parental educational levels. Native-speaking patients had higher intelligence test scores than non-native-speaking patients. Two patients, both with high baseline glycosaminoglycan levels in their urine and severe mutations in the arylsulfatase B gene, scored clearly lower than expected. Patients with pY210C performed best. Brain abnormalities were aspecific, occurring more in patients with severe symptoms.

CONCLUSION

Our study shows that cognitive development in MPS VI patients is determined not only by familial and social-background factors, but, in patients with a severe form of the disease, also by the disease itself. Therefore in patients with severe disease presentation cognition should be monitored carefully.

Enzyme therapy and immune response in relation to CRIM status: the Dutch experience in classic infantile Pompe disease

BACKGROUND

Enzyme-replacement therapy (ERT) in Pompe disease--an inherited metabolic disorder caused by acid α-glucosidase deficiency and characterized in infants by generalized muscle weakness and cardiomyopathy--can be complicated by immune responses. Infants that do not produce any endogenous acid α-glucosidase, so-called CRIM-negative patients, reportedly develop a strong response. We report the clinical outcome of our Dutch infants in relation to their CRIM status and immune response.

METHODS

Eleven patients were genotyped and their CRIM status was determined. Antibody formation and clinical outcome were assessed for a minimum of 4 years.

RESULTS

ERT was commenced between 0.1 and 8.3 months of age, and patients were treated from 0.3 to 13.7 years. All patients developed antibodies. Those with a high antibody titer (above 1:31,250) had a poor response. The antibody titers varied substantially between patients and did not strictly correlate with the patients' CRIM status. Patients who started ERT beyond 2 months of age tended to develop higher titers than those who started earlier. All three CRIM-negative patients in our study succumbed by the age of 4 years seemingly unrelated to the height of their antibody titer.

CONCLUSION

Antibody formation is a common response to ERT in classic infantile Pompe disease and counteracts the effect of treatment. The counteracting effect seems determined by the antibody:enzyme molecular stoichiometry. The immune response may be minimized by early start of ERT and by immune modulation, as proposed by colleagues. The CRIM-negative status itself seems associated with poor outcome.

Pain: a prevalent feature in patients with mucopolysaccharidosis. Results of a cross-sectional national survey

BACKGROUND

While clinical observations suggest that many patients with mucopolysaccharidosis (MPS) experience chronic pain, few studies have assessed its extent and impact. We therefore investigated its prevalence in patients with all types of MPS in the Netherlands. We also examined the association between pain and health related quality of life (HRQoL) and other clinical variables.

METHODS

We conducted a nationwide MPS survey that used questionnaires on MPS and disease-related symptoms (MPS-specific questionnaire), developmental level (Vineland Screener 0-6 years), quality of life (PedsQl and SF-36), and disability (Childhood Health Assessment Questionnaire). Depending on their age and developmental level, patients or their parents were asked to assess pain by keeping a pain diary for five consecutive days: either the Non-communicating Children's Pain Checklist - Revised (3-18 years intellectually disabled and children <8 years), the VAS-score (> 18 years), or the Faces Pain Scale - Revised (8-18 years).

RESULTS

Eighty-nine MPS patients were invited, 55 of whom agreed to participate (response rate 62 %; median age 10.9 years, range 2.9-47.2 years). They covered a wide spectrum in all age groups, ranging from no pain to severe pain. Forty percent scored above the cut-off value for pain. Most reported pain sites were the back and hips. While the MPS III group experienced the highest frequency of pain (52.9 %), 50 % of patients with an intellectual disability seemed to experience pain, versus 30 % of patients with a normal intelligence. MPS patients scored much lower (i.e., more pain) than a random sample of the Dutch population on the bodily pain domain of the SF-36 scale and the PedsQl.

CONCLUSION

With or without intellectual disabilities, many MPS patients experience pain. We recommend that standardized pain assessments are included in the regular follow-up program of patients with MPS.

The timing of introduction of pharmaceutical innovations in seven European countries

RATIONALE, AIMS AND OBJECTIVES

Differences in the performance of medical care may be due to variation in the introduction and diffusion of medical innovations. The objective of this paper is to compare seven European countries (United Kingdom, the Netherlands, West Germany, France, Spain, Estonia and Sweden) with regard to the year of introduction of six specific pharmaceutical innovations (antiretroviral drugs, cimetidine, tamoxifen, cisplatin, oxalaplatin and cyclosporin) that may have had important population health impacts.

METHODS

We collected information on introduction and further diffusion of drugs using searches in the national and international literature, and questionnaires to national informants. We combined various sources of information, both official years of registration and other indicators of introduction (clinical trials, guidelines, evaluation reports, sales statistics).

RESULTS AND CONCLUSIONS

The total length of the period between first and last introduction varied between 8 years for antiretroviral drugs and 22 years for cisplatin. Introduction in Estonia was generally delayed until the 1990s. The average time lags were smallest in France (2.2 years), United Kingdom (2.8 years) and the Netherlands (3.5 years). Similar rank orders were seen for year of registration suggesting that introduction lags are not only explained by differences in the process of registration. We discuss possible reasons for these between-country differences and implications for the evaluation of medical care.

Pain in adult patients with Pompe disease: a cross-sectional survey

BACKGROUND

Pompe disease is a rare hereditary metabolic myopathy caused by a deficiency of acid-α-glucosidase. We investigated the presence and severity of pain and its interference with daily activities in a large group of adults with Pompe disease, who we compared with an age-matched control group.

METHODS

Data were collected in a cross-sectional survey in Germany and The Netherlands. Pain was assessed using the short-form brief pain inventory (BPI). Patients also completed the Short Form-36 item (SF-36v2), the Hospital Anxiety and Depression Scale (HADS) and the Rotterdam Handicap Scale (RHS).

RESULTS

Forty-five percent of the 124 adult Pompe patients reported having had pain in the previous 24h, against 27% of the 111 controls (p=0.004). The median pain severity score in Pompe patients reporting pain was 3.1 (on a scale from 0 to 10), indicating mild pain; against 2.6 amongst controls (p=0.06). The median score of pain interference with daily activities in patients who reported pain was 3.3, against 1.3 in controls (p=0.001). Relative to patients without pain, those with pain had lower RHS scores (p=0.02), lower SF-36 Physical and Mental component summary scores (p<0.001 and p=0.049), and higher levels of depression and anxiety (p=0.005 and p=0.003).

CONCLUSIONS

To date, this is one of the largest studies on pain in a specific neuromuscular disorder. Nearly one in two Pompe patients had experienced pain in the previous 24h. Although pain severity and its interference with daily life were mild, pain was related to a reduced quality of life, less participation in daily life, and greater depression and anxiety. Its management should therefore be seen as part of clinical practice involving Pompe patients.

Enzyme replacement therapy and fatigue in adults with Pompe disease

BACKGROUND

Pompe disease is a hereditary metabolic myopathy, for which enzyme replacement therapy (ERT) has been available since 2006. We investigated whether ERT reduces fatigue in adult patients with Pompe disease.

METHODS

In this prospective international observational survey, we used the Fatigue Severity Scale (FSS) to measure fatigue. Repeated measures ANOVA was used to analyze the data over time. In a subgroup of patients, we also evaluated muscle strength using the Medical Research Council Scale, measured pulmonary function as Forced Vital Capacity, and assessed depression using the Hospital Anxiety and Depression Scale.

RESULTS

We followed 163 patients for a median period of 4 years before ERT and for 3 years during ERT. Before ERT, the mean FSS score remained stable at around 5.3 score points; during ERT, scores improved significantly by 0.13 score points per year (p < 0.001). Fatigue decreased mainly in women, in older patients and in those with shorter disease duration. Patients' improvements in fatigue were moderately correlated with the effect of ERT on depression (r 0.55; CI 95% 0.07 to 0.70) but not with the effect of ERT on muscle strength or pulmonary function.

CONCLUSIONS

Fatigue is a common and disabling problem in patients with early and advanced stages of Pompe disease. Our finding that ERT helps to reduce fatigue is therefore important for this patient population, irrespective of the mechanisms underlying this effect.

Up to five years experience with 11 mucopolysaccharidosis type VI patients

Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI, MPS VI) is a rare progressive metabolic disorder characterized by coarse facial features, hepatosplenomegaly, restrictive pulmonary function, cardiac abnormalities and stiff joints. The disease is caused by a deficiency of the lysosomal enzyme N-acetyl galactosamine 4-sulfatase which leads to glycosaminoglycan (GAG) storage in various tissues. It presents as a clinical spectrum with varying disease progressions and severities. While the phases I/II/III studies proved the effectiveness of enzyme-replacement therapy (ERT) with recombinant human arylsulfatase B, long-term data are still scarce. Over treatment periods ranging from 1.3 to 5.4 years, this prospective open-label follow-up study in 11 Dutch mucopolysaccharidosis type VI patients (age 2-18 years) showed that ERT had significant positive effects on cardiac-wall diameters (IVSd and LVMI), left and right shoulder flexions (p<0.001), liver size and spleen size (p<0.001), urinary GAG excretion (p<0.001), and the scales of quality of life (motor functioning and body functioning). ERT did not affect cardiac valve regurgitation or hearing function; HRQoL decreased slightly in two domains ('anxiety' and 'negative emotions'), and patients with the rapid and slow progressive forms of the disease differed with regard to baseline GAG excretion and GAG decrease during treatment. In conclusion, ERT had an effect on several clinical parameters. This effect was established in an open cohort of young mucopolysaccharidosis type VI patients.

Mucopolysaccharidosis type VI phenotypes-genotypes and antibody response to galsulfase

Background

Mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome; MPS VI) is an autosomal recessive lysosomal storage disorder in which deficiency of N-acetylgalactosamine 4-sulfatase (arylsulfatase B; ARSB) leads to the storage of glycosaminoglycans (GAGs) in connective tissue. The genotype-phenotype correlation has been addressed in several publications but the picture is not complete. Since 2007, enzyme-replacement therapy (ERT) has been available for patients with MPS VI in the Netherlands. The purpose of our study was to learn more about the genotype-phenotype correlations in MPS VI and the antibody response to ERT with galsulfase (recombinant human arylsulfatase B).

Methods

We identified ARSB mutations in 12 patients and used site-directed mutagenesis to study their effect. Antibody levels to galsulfase were measured using ELISA and a semi-quantitative immunoprecipitation method. We assessed the in vitro inhibitory effect of antibodies on galsulfase uptake and their effect on clinical outcome.

Results

Five patients had a rapidly progressive phenotype and seven a slowly progressive phenotype. In total 9 pathogenic mutations were identified including 4 novel mutations (N301K, V332G, A237D, and c.1142 + 2 T > C) together composing 8 pathogenic genotypes. Most mutations appeared not to affect the synthesis of ARSB (66 kD precursor), but to hamper its maturation (43 kD ARSB). Disease severity was correlated with urinary GAG excretion. All patients developed antibodies to galsulfase within 26 weeks of treatment. It was demonstrated that these antibodies can inhibit the uptake of galsulfase in vitro.

Conclusions

The clinical phenotypes and the observed defects in the biosynthesis of ARSB show that some of the mutations that we identified are clearly more severe than others. Patients receiving galsulfase as enzyme-replacement therapy can develop antibodies towards the therapeutic protein. Though most titers are modest, they can exceed a level at which they potentially affect the clinical outcome of enzyme-replacement therapy.

Impact of enzyme replacement therapy on survival in adults with Pompe disease: results from a prospective international observational study

Background

Pompe disease is a rare metabolic myopathy for which disease-specific enzyme replacement therapy (ERT) has been available since 2006. ERT has shown efficacy concerning muscle strength and pulmonary function in adult patients. However, no data on the effect of ERT on the survival of adult patients are currently available. The aim of this study was to assess the effect of ERT on survival in adult patients with Pompe disease.

Methods

Data were collected as part of an international observational study conducted between 2002 and 2011, in which patients were followed on an annual basis. Time-dependent Cox’s proportional hazards models were used for univariable and multivariable analyses.

Results

Overall, 283 adult patients with a median age of 48 years (range, 19 to 81 years) were included in the study. Seventy-two percent of patients started ERT at some time during follow-up, and 28% never received ERT. During follow-up (median, 6 years; range, 0.04 to 9 years), 46 patients died, 28 (61%) of whom had never received ERT. After adjustment for age, sex, country of residence, and disease severity (based on wheelchair and ventilator use), ERT was positively associated with survival (hazard ratio, 0.41; 95% CI, 0.19 to 0.87).

Conclusion

This prospective study was the first to demonstrate the positive effect of ERT on survival in adults with Pompe disease. Given the relatively recent registration of ERT for Pompe disease, these findings further support its beneficial impact in adult patients.

Innovations in medical care and mortality trends from four circulatory diseases between 1970 and 2005

BACKGROUND

Governments have identified innovation in pharmaceuticals and medical technology as a priority for health policy. Although the contribution of medical care to health has been studied extensively in clinical settings, much less is known about its contribution to population health. We examine how innovations in the management of four circulatory disorders have influenced trends in cause-specific mortality at the population level.

METHODS

Based on literature reviews, we selected six medical innovations with proven effectiveness against hypertension, ischaemic heart disease, heart failure and cerebrovascular disease. We combined data on the timing of these innovations and cause-specific mortality trends (1970-2005) from seven European countries. We sought to identify associations between the introduction of innovations and favourable changes in mortality, using Joinpoint-models based on linear spline regression.

RESULTS

For both ischaemic heart disease and cerebrovascular disease, the timing of medical innovations was associated with improved mortality in four out of five countries and five out of seven countries, respectively, depending on the innovation. This suggests that innovation has impacted positively on mortality at the population level. For hypertension and heart failure, such associations could not be identified.

CONCLUSION

Although improvements in cause-specific mortality coincide with the introduction of some innovations, this is not invariably true. This is likely to reflect the incremental effects of many interventions, the time taken for them to be adopted fully and the presence of contemporaneous changes in disease incidence. Research on the impact of medical innovations on population health is limited by unreliable data on their introduction.

Amenable mortality revisited: the AMIEHS study

OBJECTIVES

There is a renewed interest in health system indicators. In 1976 a measure of quality of healthcare, amenable mortality, was introduced by Rutstein. This indicator is based on the concept that deaths from certain causes should not occur in the presence of timely and effective healthcare. In the project "Amenable mortality in the European Union: toward better indicators for the effectiveness of health systems" (AMIEHS), we introduce a new approach to the selection of indicators of amenable mortality.

METHODS

Based on predefined selection criteria and a broad review of the literature on the effectiveness of medical interventions, a first set of potential indicators of amenable mortality (causes of death) was selected. The timing of the introduction of medical innovations was established through reviews and questionnaires sent to national experts from seven participating European countries. The preselected indicators were then validated by a trend analysis that identified associations between the timing of innovations and cause-specific mortality trends and by a Delphi-procedure.

RESULTS

After a short review of previous lists of amenable mortality indicators and a detailed description of the innovative procedure in the AMIEHS project we present a list of 14 causes of death that passed our selection criteria. We illustrate our empirical validation of these indicators using the examples of peptic ulcer and renal failure.

CONCLUSIONS

The innovation developed in the AMIEHS study is a rigorous new approach to the concept of amenable mortality that includes empirical validation. Only validated indicators can be successfully used to assess the quality of healthcare systems in international comparisons.

Treatment options for lysosomal storage disorders: developing insights

INTRODUCTION

Lysosomal storage disorders (LSDs) are clinically heterogeneous disorders that result primarily from lysosomal accumulation of macromolecules in various tissues. LSDs are always progressive, and often lead to severe symptoms and premature death. The identification of the underlying genetic and enzymatic defects has prompted the development of various treatment options.

AREAS COVERED

To describe the current treatment options for LSDs, the authors provide a focused overview of their pathophysiology. They discuss the current applications and challenges of enzyme-replacement therapy, stem-cell therapy, gene therapy, chaperone therapy and substrate-reduction therapy, as well as future therapeutic prospects.

EXPERT OPINION

Over recent decades, considerable progress has been made in the treatment of LSDs and in the outcome of patients. None of the current options are completely curative yet. They are complicated by the difficulty in efficiently targeting all affected tissues (particularly the central nervous system), in reaching sufficiently high enzyme levels in the target tissues, and by their high costs. The pathways leading from the genetic mutation to the clinical symptoms should be further elucidated, as they might prompt the development of new and ultimately curative therapies.

Using 'amenable mortality' as indicator of healthcare effectiveness in international comparisons: results of a validation study

BACKGROUND AND STUDY AIMS

There is widespread consensus on the need for better indicators of the effectiveness of healthcare. We carried out an analysis of the validity of amenable mortality as an indicator of the effectiveness of healthcare, focusing on the potential use in routine surveillance systems of between-country variations in rates of mortality. We assessed whether the introduction of specific healthcare innovations coincided with declines in mortality from potentially amenable causes in seven European countries. In this paper, we summarise the main results of this study and illustrate them for four conditions.

DATA AND METHODS

We identified 14 conditions for which considerable declines in mortality have been observed and for which there is reasonable evidence in the literature of the effectiveness of healthcare interventions to lower mortality. We determined the time at which these interventions were introduced and assessed whether the innovations coincided with favourable changes in the mortality trends from these conditions, measured using Poisson linear spline regression. All the evidence was then presented to a Delphi panel.

MAIN RESULTS

The timing of innovation and favourable change in mortality trends coincided for only a few conditions. Other reasons for mortality decline are likely to include diffusion and improved quality of interventions and in incidence of diseases and their risk factors, but there is insufficient evidence to differentiate these at present. For most conditions, a Delphi panel could not reach consensus on the role of current mortality levels as measures of effectiveness of healthcare.

DISCUSSION AND CONCLUSIONS

Improvements in healthcare probably lowered mortality from many of the conditions that we studied but occurred in a much more diffuse way than we assumed in the study design. Quantification of the contribution of healthcare to mortality requires adequate data on timing of innovation and trends in diffusion and quality and in incidence of disease, none of which are currently available. Given these gaps in knowledge, between-country differences in levels of mortality from amenable conditions should not be used for routine surveillance of healthcare performance. The timing and pace of mortality decline from amenable conditions may provide better indicators of healthcare performance.

Socioeconomic inequalities in mortality from conditions amenable to medical interventions: do they reflect inequalities in access or quality of health care?

Background

Previous studies have reported large socioeconomic inequalities in mortality from conditions amenable to medical intervention, but it is unclear whether these can be attributed to inequalities in access or quality of health care, or to confounding influences such as inequalities in background risk of diseases. We therefore studied whether inequalities in mortality from conditions amenable to medical intervention vary between countries in patterns which differ from those observed for other (non-amenable) causes of death. More specifically, we hypothesized that, as compared to non-amenable causes, inequalities in mortality from amenable causes are more strongly associated with inequalities in health care use and less strongly with inequalities in common risk factors for disease such as smoking.

Methods

Cause-specific mortality data for people aged 30–74 years were obtained for 14 countries, and were analysed by calculating age-standardized mortality rates and relative risks comparing a lower with a higher educational group. Survey data on health care use and behavioural risk factors for people aged 30–74 years were obtained for 12 countries, and were analysed by calculating age-and sex-adjusted odds ratios comparing a low with a higher educational group. Patterns of association were explored by calculating correlation coefficients.

Results

In most countries and for most amenable causes of death substantial inequalities in mortality were observed, but inequalities in mortality from amenable causes did not vary between countries in patterns that are different from those seen for inequalities in non-amenable mortality. As compared to non-amenable causes, inequalities in mortality from amenable causes are not more strongly associated with inequalities in health care use. Inequalities in mortality from amenable causes are also not less strongly associated with common risk factors such as smoking.

Conclusions

We did not find evidence that inequalities in mortality from amenable conditions are related to inequalities in access or quality of health care. Further research is needed to find the causes of socio-economic inequalities in mortality from amenable conditions, and caution should be exercised in interpreting these inequalities as indicating health care deficiencies.

Prenatal diagnosis for haemophilia: a nationwide survey among female carriers in the Netherlands

Carriers of haemophilia face difficult choices regarding prenatal diagnosis, but little is known about the determinants that influence their decisions. The aim of this study was to assess the incidence of prenatal diagnosis and potential determinants affecting the choice for prenatal diagnosis. A nationwide survey was performed among all women who underwent carriership testing for haemophilia in the Netherlands between 1992 and 2004. Prenatal diagnosis was assessed in 207 carriers of haemophilia A or B who had been pregnant. Prenatal diagnosis was categorized into early first trimester (Y-PCR testing or chorionic villus sampling) often intended to prevent the birth of a child with haemophilia, and into late prenatal diagnosis (amniocentesis or ultrasound assessment) aimed at obstetrical management. Of 207 carriers 112 (54%) underwent prenatal diagnosis. Forty-eight women underwent early prenatal diagnosis and 64 women underwent late prenatal diagnosis. In 26 pregnancies early prenatal diagnosis was positive for haemophilia, and in 18 of these pregnancies termination was opted for. The choice for early prenatal diagnosis was associated with a liberal view towards termination of pregnancy (relative risk (RR) 12.5; 95% confidence interval (CI) 3.1-51.2), severe haemophilia in the family (RR 20.2; CI 2.7-153.6), absence of a religion (RR 1.9; CI 1.1-3.1) and older age (RR 2.0; CI 1.0-3.9). The choice for late prenatal diagnosis was associated with birth year after 1970 (RR 2.3; CI 1.5-3.5) and a previous child with haemophilia (RR 2.2; CI 1.4-3.4). More than half of all Dutch haemophilia carriers underwent prenatal diagnosis. Several determinants were strongly associated with prenatal diagnosis.

Cause-specific mortality time series analysis: a general method to detect and correct for abrupt data production changes

BACKGROUND

Monitoring the time course of mortality by cause is a key public health issue. However, several mortality data production changes may affect cause-specific time trends, thus altering the interpretation. This paper proposes a statistical method that detects abrupt changes ("jumps") and estimates correction factors that may be used for further analysis.

METHODS

The method was applied to a subset of the AMIEHS (Avoidable Mortality in the European Union, toward better Indicators for the Effectiveness of Health Systems) project mortality database and considered for six European countries and 13 selected causes of deaths. For each country and cause of death, an automated jump detection method called Polydect was applied to the log mortality rate time series. The plausibility of a data production change associated with each detected jump was evaluated through literature search or feedback obtained from the national data producers.For each plausible jump position, the statistical significance of the between-age and between-gender jump amplitude heterogeneity was evaluated by means of a generalized additive regression model, and correction factors were deduced from the results.

RESULTS

Forty-nine jumps were detected by the Polydect method from 1970 to 2005. Most of the detected jumps were found to be plausible. The age- and gender-specific amplitudes of the jumps were estimated when they were statistically heterogeneous, and they showed greater by-age heterogeneity than by-gender heterogeneity.

CONCLUSION

The method presented in this paper was successfully applied to a large set of causes of death and countries. The method appears to be an alternative to bridge coding methods when the latter are not systematically implemented because they are time- and resource-consuming.

Prospective evaluation of the clinical utility of quantitative bleeding severity assessment in patients referred for hemostatic evaluation

BACKGROUND

Quantitative bleeding assessment tools (BATs) have been used to describe the severity of the bleeding phenotype in patients with von Willebrand disease.

OBJECTIVES

To evaluate the clinical usefulness of a BAT for the diagnosis of mild bleeding disorders (MBDs) in previously undiagnosed patients.

METHODS

We prospectively assessed 215 patients who were consecutively referred for evaluation of bleeding symptoms (n=71), abnormal laboratory clotting test results (n=105) or family investigation (n=39) at two second-level centers. The bleeding history was assessed by a young investigator who administered the BAT instrument, and also by a senior physician who independently evaluated the patient and made the final diagnoses. Sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) were computed for a predefined bleeding score (BS) cut-off (BS of >3). Receiver operating characteristic curves were used to establish a diagnostic prediction rule.

RESULTS

Assuming the prevalence of MBD in the general population to be ∼1%, a normal BS (≤3) had a very high NPV (99.2%). The PPVs in patients referred for hemostatic or family evaluation at second-level clinics were estimated to be 71.0% and 77.5% (assuming MDB prevalences of 20% and 50%, respectively, in these settings). Measurement of BS in addition to activated partial thromboplastin time significantly increased the diagnostic efficiency of the BAT instrument (NPV of 99.6%).

CONCLUSIONS

BAT use improves the evaluation of patients with suspected MBD, and we propose its use in a clinical prediction guide based on BAT and activated partial thromboplastin time for the exclusion of patients with suspected MBD in a low-prevalence setting.

Analysis of low frequency bleeding data: the association of joint bleeds according to baseline FVIII activity levels

Many studies in the field of haemophilia and other coagulation deficiencies require analyses of bleeding frequencies. In haemophilia, the association of bleeding frequency with factor VIII (FVIII) activity levels is known from experience, but significant results are lacking. Bleeding frequencies in haemophilia are highly skewed count data, with large proportions of zeros. Both the skewness and the high amount of zeros pose a problem for standard (linear) modelling techniques. This study investigated the optimal analysing strategy for bleeding data by using the association of residual clotting factor level and number of joint bleeds in moderate and mild patients treated on demand as example. In total, 433 patients with moderate (27%) and mild (73%) haemophilia A treated on demand were included in this study. One year of self-reported data on joint bleed frequency and baseline clotting factor activity were analysed using Poisson, negative binomial, zero-inflated Poisson, and zero-inflated negative binomial distributions. Multivariate regression analysis using negative binomial distribution provided the optimum data analytical strategy. This model showed 18% reduction [Rate ratio (RR) 0.82; 95%confidence interval (CI) 0.77-0.86] of bleeding frequency with every IU dL(-1) increase in residual FVIII activity. The actual association is expected to be higher because of exclusion (30 out of 463 patients) of patients on prophylaxis (baseline FVIII levels 0.01-0.06 IU mL(-1)). The best way to analyse low frequency bleeding data is using a negative binomial distribution.

Bleeding in carriers of hemophilia

A wide range of factor VIII and IX levels is observed in heterozygous carriers of hemophilia as well as in noncarriers. In female carriers, extreme lyonization may lead to low clotting factor levels. We studied the effect of heterozygous hemophilia carriership on the occurrence of bleeding symptoms. A postal survey was performed among most of the women who were tested for carriership of hemophilia in the Netherlands before 2001. The questionnaire included items on personal characteristics, characteristics of hemophilia in the affected family members, and carrier testing and history of bleeding problems such as bleeding after tooth extraction, bleeding after tonsillectomy, and other operations. Information on clotting factor levels was obtained from the hospital charts. Logistic regression was used to assess the relation of carrier status and clotting factor levels with the occurrence of hemorrhagic events. In 2004, 766 questionnaires were sent, and 546 women responded (80%). Of these, 274 were carriers of hemophilia A or B. The median clotting factor level of carriers was 0.60 IU/mL (range, 0.05-2.19 IU/mL) compared with 1.02 IU/mL (range, 0.45-3.28 IU/mL) in noncarriers. Clotting factor levels from 0.60 to 0.05 IU/mL were increasingly associated with prolonged bleeding from small wounds and prolonged bleeding after tooth extraction, tonsillectomy, and operations. Carriers of hemophilia bleed more than other women, especially after medical interventions. Our findings suggest that not only clotting factor levels at the extreme of the distribution, resembling mild hemophilia, but also mildly reduced clotting factor levels between 0.41 and 0.60 IU/mL are associated with bleeding.

Mortality and causes of death in patients with hemophilia, 1992-2001: a prospective cohort study

BACKGROUND

Clotting factor products have been safe for HIV since 1985, and for hepatitis C since 1992. Few studies have reported on mortality in the total population of hemophilia patients after the period of risk of viral infection transmission.

OBJECTIVES

We studied the mortality, causes of death, and life expectancy of hemophilia patients between 1992 and 2001. We compared these findings with those of previous cohorts, together spanning the periods before, during, and after the use of potentially contaminated clotting products.

PATIENTS AND METHODS

We performed a prospective cohort study among 967 patients with hemophilia A and B. Death rates, overall and cause-specific, were compared with national mortality figures for males adjusted for age and calendar period as standardized mortality ratio (SMRs).

RESULTS

Between 1992 and 2001, 94 (9.7%) patients had died and two patients were lost to follow-up (0.2%). Mortality was 2.3-times higher in hemophilia patients than in the general male population (SMR 2.3 95% confidence interval 1.9-2.8). In patients with severe hemophilia, life expectancy decreased from 63 (1972-1985) to 59 years (1992-2001). Exclusion of virus-related deaths resulted in a life expectancy at birth of 72 years.

CONCLUSIONS

AIDS was the main cause of death (26%) and 22% of deaths were because of hepatitis C. In patients not affected by viral infections, there still appeared to be a trend toward a moderately increased mortality compared with the Dutch male population. Thus, mortality of patients with hemophilia is still increased; this is largely because of the consequences of viral infections.

Hepatitis C and health-related quality of life among patients with hemophilia

Hepatitis C has a negative effect on health-related quality of life (HRQoL). It is not clear whether hepatitis C affects HRQoL of patients with hemophilia. The objective of this study was to assess the effect of hepatitis C virus (HCV) infection on HRQoL in patients with hemophilia. A cross-sectional study was performed among all registered hemophilia patients in the Netherlands. HRQoL was determined by using the self-administered SF-36 questionnaire. Patients were eligible for the study if they completed the SF-36, had been treated with clotting factor products before 1992, and had reported their hepatitis C status. Data on the severity of hemophilia were obtained from the hemophilia treatment centers. The validity of the self-reported data on hepatitis C status was verified in a random sample of 92 (15%) patients; 92% reported their hepatitis C status correctly. Fifty-five percent (333/602) of the study population had a current HCV infection. All eight domains of the SF-36 were lower in patients with a current HCV infection than they were in patients who had never been infected with HCV. After adjustment for age, severity of hemophilia, human immunodeficiency virus (HIV) status, employment status, and joint limitations, hepatitis C infection was associated with a decrease of HRQoL on the domains of general health (difference 6.9 [95% confidence interval (C.I.) 2.7 to 11.2]) and vitality (3.8 [95% C.I. 0.1 to 7.7]). Hemophilia patients infected with HCV scored lower on the HRQoL domains of general health and vitality than hemophilia patients who had never been infected with HCV.

Hepatitis C infection among Dutch haemophilia patients: a nationwide cross-sectional study of prevalence and antiviral treatment

Hepatitis C is a major co-morbidity among patients with haemophilia who received inadequately or non-virus-inactivated clotting factor concentrates before 1992. The objectives of this study were to investigate the prevalence of hepatitis C and the use of antiviral therapies during the last decade among patients with haemophilia in the Netherlands. We performed a cross-sectional study and a questionnaire was sent to all 1519 patients known with haemophilia in the Netherlands between 2001 and 2002. The study population for the present study consisted of 771 patients who had received clotting factor products before 1992 of whom 638 reported their hepatitis C status. In total, 441 of the 638 (68%) patients ever had a positive test for hepatitis C virus (HCV); 344 patients (54%) had a current infection, and 97 (15%) had cleared the virus. Among 344 patients currently HCV infected, 111 (32%) had received treatment for hepatitis C, while 34% (33/97) of patients with an infection in the past had been treated for hepatitis C. In 2002 the prevalence of hepatitis C among patients with haemophilia who received clotting factor products before 1992 was 54%. The majority of patients with a current HCV infection had not been treated with antiviral therapy.

Thirty years of hemophilia treatment in the Netherlands, 1972-2001

Since the introduction of replacement therapy in the early 1960s by the infusion of plasma-derived factor VIII and IX preparations, important changes have occurred for hemophilia patients. We studied the medical and social developments over 30 years of hemophilia treatment. Since 1972, 5 cross-sectional national postal surveys among all hemophilia patients in the Netherlands were performed, the latest in 2001. The prestructured questionnaires included items on treatment, the presence of inhibitory antibodies against factor VIII or IX, the annual number of bleeding episodes, use of inpatient hospital care, and hepatitis C and HIV infections. Response rate in 2001 was 70%. Young patients (<16 years) with severe hemophilia showed the largest increase in use of prophylaxis, from 34% in 1972 to 86% in 2001. The occurrence of hemorrhages has gradually decreased. Hospital admissions decreased from 47% of all patients in 1972 to 18% in 2001. Our study shows that the treatment of patients with severe hemophilia in the Netherlands has focused on the use of prophylactic treatment, especially in children. This has resulted in a decrease in bleeding frequency and an improvement of the medical and social circumstances of patients.

The uptake of recombinant Factor VIII in the Netherlands

In comparison with other biotechnology substitutions, the adoption of recombinant Factor VIII (rFVIII) has been relatively slow. We sent a postal questionnaire to all Dutch haemophilia patients and haemophilia-treating physicians, to determine which factors predict whether a patient uses plasma-derived FVIII (pdFVIII) or rFVIII and to investigate patients' and doctors' opinions on both products. Fifty-six per cent of patients received rFVIII. This percentage varied widely between centres. Only one doctor would choose to use pdFVIII if he suffered from haemophilia A himself, and 74% would choose to use rFVIII. Younger patients, those not infected with the human immunodeficiency virus or hepatitis C, and those who did not have family members who used pdFVIII switched more often from pdFVIII to rFVIII. Patients who rated themselves as innovative, who had family members who used rFVIII, and those who were treated in a large haemophilia treatment centre were also more likely to have switched. For physicians and patients alike, the respondents generally did not see large differences between rFVIII and pdFVIII, except for the risk of infections and the knowledge of long-term effects (both larger for pdFVIII). Although haemophilia patients represent one of the most empowered patient groups, physicians appear to have been influential in choosing between pdFVIII and rFVIII.