Pharmacogenomic testing in paediatrics: clinical implementation strategies

Pharmacogenomics (PGx) relates to the study of genetic factors determining variability in drug response. Implementing PGx testing in paediatric patients can enhance drug safety, helping to improve drug efficacy or reduce the risk of toxicity. Despite its clinical relevance, the implementation of PGx testing in paediatric practice to date has been variable and limited.

As with most paediatric pharmacological studies, there are well‐recognised barriers to obtaining high‐quality PGx evidence, particularly when patient numbers may be small, and off‐label or unlicensed prescribing remains widespread. Furthermore, trials enrolling small numbers of children can rarely, in isolation, provide sufficient PGx evidence to change clinical practice, so extrapolation from larger PGx studies in adult patients, where scientifically sound, is essential.

This review paper discusses the relevance of PGx to paediatrics and considers implementation strategies from a child health perspective. Examples are provided from Canada, the Netherlands and the UK, with consideration of the different healthcare systems and their distinct approaches to implementation, followed by future recommendations based on these cumulative experiences.

Improving the evidence base demonstrating the clinical utility and cost‐effectiveness of paediatric PGx testing will be critical to drive implementation forwards. International, interdisciplinary collaborations will enhance paediatric data collation, interpretation and evidence curation, while also supporting dedicated paediatric PGx educational initiatives. PGx consortia and paediatric clinical research networks will continue to play a central role in the streamlined development of effective PGx implementation strategies to help optimise paediatric pharmacotherapy.

An initial health economic evaluation of pharmacogenomic testing in patients treated for childhood cancer with anthracyclines

BACKGROUND

Anthracyclines are a class of highly effective chemotherapeutic drugs commonly used to treat cancer patients. Anthracyclines, however, are associated with the development of serious adverse reactions, including anthracycline-induced cardiotoxicity (ACT). It is not possible, within current practice, to accurately individualize treatment to minimize risk.

PROCEDURE

Recently, genetic variants have been associated with the risk of ACT in children. Building on these findings and the related genetic test, a predictive model was developed which classifies pediatric patients by their risk of developing ACT. We assessed the value of this ACT-predictive risk classification in addressing ACT.

RESULTS

With current care, the estimated average lifetime cost of ACT is $8,667 per anthracycline-treated patient and approximately 7% of patients are expected to die from ACT. The projected impact of the information from the new predictive model is a 17% reduction in the risk of mortality from ACT and savings of about 6%: lives saved and lower costs.

CONCLUSION

The newly identified genetic variants associated with the risk of ACT provide information that allows a more reliable prediction of the risk of ACT for a given patient and can be obtained at a very moderate cost, which is expected to lead to meaningful progress in reducing harm and costs associated with ACT.

Physician and parent barriers to the use of oral corticosteroids for the prevention of paediatric URTI-induced acute asthma exacerbations at home

Objectives

Administration of oral corticosteroids at the onset of an upper respiratory tract infection (URTI) can be effective in the management of acute asthma exacerbations in children. This study was designed to identify barriers to parent-initiated implementation of clinical practice guideline-recommended use of oral corticosteroids for prophylaxis against severe asthma exacerbations in children.

Methods

Twenty-seven children who presented to BC Children's Hospital with URTI-induced asthma exacerbations were recruited. Parents received a filled prescription for a course of oral corticosteroids to be used at the earliest onset of their child's next URTI. Each family was contacted monthly over a 1-year period to inquire about URTI events, asthma symptoms, medication use and health care utilization. Focus groups were held with family physicians, paediatricians and parents; transcripts were analyzed qualitatively to identify key themes.

Results

Incidence of URTI events among participants was high (85%). Uptake of study medication was low; 44% used the medication as directed at their first URTI event. Eleven per cent of the patients who used the study medication also visited the emergency department for an exacerbation. Focus groups identified four main barriers to the effective use of parent-initiated oral corticosteroids: physician resistance and conflicting messages from providers; parent uncertainty about oral corticosteroids; multiple caregivers and relative ease of access to an emergency department.

Conclusion

We have identified key barriers to the effective use of parent-administered oral corticosteroids as an asthma management strategy and gained important insights regarding the research that is required to enhance the applicability of the strategy.

Asthma in British Columbia: Are we finally breathing easier? A population-based study of the burden of disease over 14 years

OBJECTIVE

Asthma presents a significant global burden, but whether the incidence and prevalence of asthma is rising is still debated. The objective of this study was to determine the prevalence and incidence of asthma in British Columbia (BC), Canada, and characterize associated health services utilization.

METHODS

We extracted data from provincial administrative hospitalization, medical services, and prescription drug databases for patients aged 5 to 55 years, during 1996 to 2009 having ≥270 MSP registration days and meeting asthma definition of: ≥1 hospital admissions with asthma as the principal diagnosis, or ≥2 physician visits for asthma as the principal diagnosis, or ≥3 asthma drug dispensings. Regression models were used to test change in asthma incidence and prevalence, and use of various health care services, such as physician and emergency department (ED) visits, and hospitalizations.

RESULTS

379,950 patients met the study criteria. The prevalence (2.6%) and incidence (0.7%) of asthma was relatively stable over the study period. There was a decline in proportion of patients visiting family practitioners (FP) (OR 0.92; 95% CI 0.90-0.94), specialists (OR 0.60; 95% CI 0.58-0.62), using ED services (OR 0.31; 95% CI 0.30-0.32) and hospitalizations (OR 0.34; 95% CI 0.31-0.37). Regional differences were noted, with lower rates of FP and specialist visits and higher rates of ED visits for asthma in rural versus urban areas.

CONCLUSIONS

In BC, the incidence and prevalence of asthma has remained stable over 14 years. Although health service utilization declined, there is variation between rural and urban regions.

Effectiveness of rehabilitation programs on a remainder population: a retrospective analysis

Retrospective analyses were conducted on a remainder population of 361 individuals with mental retardation at a rehabilitation institute. Program effectiveness was determined by means of aggregate and individual changes in performance on several instruments. Psychometric tests showed no significant increases in test scores whereas gains were found on all adaptive functioning instruments. Programs dealing with daily living and more conceptual material appeared to be more effective than vocational programs. One third of the remainder clients gained from the institute's programs.

Measuring oscillatory potential during the course of an arterial occlusion: a method based on Fourier analysis

Recently we developed a quantitative method of measuring the Oscillatory Potentials (OP's) for a clinical study in diabetic patients. Several problems were experienced in interpreting the results obtained with digital filtering. The main dilemma was the separation of the first OP from the a-wave, since their frequencies are within the same range. The fast Fourier transform (FFT) was applied for this purpose. From the FFT response the power of the OP's was calculated and expressed in microwatts. The advantage of this method is clearly demonstrated in the case of a patient with central retinal arterial occlusion.

Measuring oscillatory potentials: Fourier analysis

Studying the oscillatory potentials in diabetic retinopathy, the authors experienced several problems interpreting results of digital filtering. The main problem was the separation of the first potential from the a-wave, since their frequencies are within the same range. To improve the procedure of measuring implicit times and of calculating amplitudes, the filtering was started with a finite impulse response filter and followed by a fast Fourier transform. The power of the oscillatory potential was calculated by determining the dominant frequency in the Fourier transformed response and expressed in microwatts. A group of normal subjects was compared with a group of early diabetic retinopathy patients. It appears that even in pathological circumstances a quantitative expression of the oscillatory potential is possible.

Performance of adults with developmental handicaps on alternate forms of the Peabody Picture Vocabulary Test

A total of 154 adults with developmental handicaps involved in a comprehensive community-based habilitation program were tested on alternate forms of the PPVT and PPVT--Revised to determine interest reliabilities. A comparison of response profiles indicated that there was a significant degree of correspondence in general performance using alternate forms (p less than .0001). This correspondence was maintained regardless of whether overall raw score or mental age equivalents were used. However, a comparison of performance on individual test items that were identical on alternate forms showed less consistent results. Particular aspects of the administration and structure of the PPVT/PPVT-R and response characteristics of individuals with developmental handicaps are suggested as being important factors in test administration and interpretation with this population.

Mental development of adults with Down syndrome

Measures of cognitive, verbal, and functional performance obtained at widely separated time periods were examined for adults with Down syndrome. Comparisons of first and last test profiles for Raven Coloured Progressive Matrices, Peabody Picture Vocabulary Test, and Adaptive Functioning Index (Social Education) Test all demonstrated significant increases over a mean time span of 5 years. These increases could not be attributed to year of entry into program, history of institutionalization, or age of the individuals. The findings indicate that mental development of adults with Down syndrome continues well into the third and fourth decade of life.