Navigating social determinants of health barriers in the management of phenylketonuria

Phenylketonuria (PKU) is an inborn error of amino acid metabolism that is typically identified by newborn screening. With lifelong treatment consisting of dietary management, frequent laboratory monitoring, and regular metabolic clinic visits, patients with PKU can maintain good health and metabolic control. Here, we describe the case of an 8-year-old patient with PKU who has been followed by a metabolic clinic since birth. Despite responsiveness to sapropterin, this patient has had periods of poor metabolic control throughout her life due to her family's economic hardships, including limited access to transportation, housing, food, and health insurance. This case illustrates how social determinants of health may negatively affect rare disease management and potential strategies for addressing barriers to care.

Poor adherence during adolescence is a risk factor for becoming lost-to-follow-up in patients with phenylketonuria

Purpose

A high rate of lost to follow-up (LTFU) in patients with phenylketonuria (PKU) represents a main challenge. In this study, we investigated potential risk factors for becoming LTFU related to adolescence as a critical period of life.

Methods

We retrospectively analyzed longitudinal data collected from 1993 to 2019 of patients diagnosed with classic PKU that were followed at our center during adolescence (14-18 y) and at least once in adulthood (>18 y). Patients who interrupted their contact with our center after the 18th birthday for at least 2 years were classified as LTFU. We performed a multivariate regression analysis to investigate following potential risk factors for becoming LTFU in adult life: sex, dietary compliance during adolescence assessed through the mean of the annual medians of phenylalanine plasma values, average number of contacts with the center during adolescence and age at first visit after the 18th birthday.

Results

93 patients (52 males, 41 females) were included in the study. 58% became LTFU during adulthood. The mean age at the last visit before becoming LTFU was 26.2 ± 5.1 years. In the multivariate Cox regression analysis we found that poor dietary compliance during adolescence was significantly associated with a higher risk of becoming LTFU during adulthood (p-value = 0.028).

Discussion

Adult patients who displayed poor treatment adherence during adolescence should be identified and carefully monitored to prevent loss of contact.

Adult PKU Clinics in the UK-Users' Experiences and Perspectives

Adults with PKU require life-long management, and ideally, their care should be in a specialised adult metabolic clinic. Their outcomes and co-morbidities have received much attention, but data are lacking on their experience, satisfaction and expectations about the care they receive. This survey reports the experiences and care adults with PKU receive from specialist metabolic clinics in the UK. The online survey developed by the UK NSPKU (National Society for Phenylketonuria), was placed on the NSPKU website from February 2021 to December 2022, and was completed by adults with PKU (≥18 years) or their carers/family members. Sixty-five adult PKU patients and 9 caregivers of adult patients completed the questionnaire (63% female in total). Only 32% of respondents were following a Phe-restricted diet with protein substitute intake as prescribed; the rest were partially adherent or not on dietary restrictions. Nineteen per cent (n = 14/74) had not been reviewed in clinic for two years. Half of the respondents (50%) described their experience in adult clinics as "good". Half of the patients were unable to contact their dietitians with questions or concerns, and only 24% considered that they received adequate support. Clinic reviews usually included anthropometric (82%) and dietary assessments (64%), discussion on management of PKU in daily life (78%) and a blood test (71%). Eighty-eight per cent reported they had at least one neurocognitive, mental health or behavioural co-morbidity but less than half of the patients reported an assessment on their neurocognitive functioning or mental health issues. Adult male patients appeared to have less detailed clinic review than females. Less than half (44%) of the respondents reported that they performed a blood spot for blood Phe at least monthly, but only 32% considered they had been informed about the risk of high Phe levels in adulthood. Although time, cost and stress related to travelling were barriers to a face-to-face review, more than 40% of patients had concerns about remote appointments. The frequency and extent of monitoring of adults with PKU, attending specialist adult services, were less than those specified by the PKU European guidelines. The care of women of reproductive age is prioritised over men. Adult metabolic health services require further attention, development and resources to provide a high standard and equitable service to patients with PKU.

Expert Consensus on the Long-Term Effectiveness of Medical Nutrition Therapy and Its Impact on the Outcomes of Adults with Phenylketonuria

Many adults with phenylketonuria (PKU) rely on medical nutrition therapy (MNT; low phenylalanine (Phe) diet with protein substitutes/medical foods) to maintain blood Phe concentrations within recommended ranges and prevent PKU-associated comorbidities. Despite disease detection through newborn screening and introduction of MNT as early as birth, adherence to MNT often deteriorates from childhood onwards, complicating the assessment of its effectiveness in the long term. Via a modified Delphi process, consensus (≥70% agreement) was sought on 19 statements among an international, multidisciplinary 13-member expert panel. After three iterative voting rounds, the panel achieved consensus on 17 statements related to the limitations of the long-term effectiveness of MNT (7), the burden of long-term reliance on MNT (4), and its potential long-term detrimental health effects (6). According to the expert panel, the effectiveness of MNT is limited in the long term, is associated with a high treatment burden, and demonstrates that adults with PKU are often unable to achieve metabolic control through dietary management alone, creating an unmet need in the adult PKU population.

Characterisation and differential diagnosis of neurological complications in adults with phenylketonuria: literature review and expert opinion

OBJECTIVE

Phenylketonuria (PKU) is a rare inherited metabolic disorder characterised by elevated phenylalanine (Phe) concentrations that can exert neurotoxic effects if untreated or upon treatment discontinuation. This systematic review supported by expert opinion aims to raise awareness among the neurological community on neurological complications experienced by adults with PKU (AwPKU).

METHODS

The PubMed database was searched for articles on neurological signs and symptoms in AwPKU published before March 2022. In addition, two virtual advisory boards were held with a panel of seven neurologists and two metabolic physicians from Germany and Austria. Findings are supported by three illustrative patient cases.

RESULTS

Thirty-nine articles were included. Despite early diagnosis and treatment, neurological signs and symptoms (e.g. ataxia, brisk tendon reflexes, tremor, visual impairment) can emerge in adulthood, especially if treatment has been discontinued after childhood. In PKU, late-onset neurological deficits often co-occur with cognitive impairment and psychiatric symptoms, all of which can be completely or partially reversed through resumption of treatment.

CONCLUSION

Ideally, neurologists should be part of the PKU multidisciplinary team, either to bring lost to follow-up patients back to clinic or to manage symptoms in referred patients, considering that symptoms are often reversible upon regaining metabolic control. The current findings have been combined in a leaflet that will be disseminated among neurologists in Germany and Austria to create awareness.

Measuring Burden of Illness in Phenylketonuria (PKU): Development of the PKU Symptom Severity and Impacts Scale as a Robust Patient-Reported Outcome

Introduction

Phenylketonuria (PKU) is a rare, metabolic genetic disorder that can cause various neuropsychological symptoms that often affect patients’ health-related quality of life, even for patients with good metabolic control. To date, no patient-reported outcomes (PRO) instrument combines the measurement of neuropsychological and dietary concepts to capture the broad impact of PKU on quality of life. This article presents the development of the PKU Symptom Severity and Impacts Scale (PKU-SSIS), a PRO instrument that is designed to evaluate neuropsychological symptoms and impacts in early-treated patients with PKU.

Methods

A draft instrument was developed based on a targeted literature review, PKU expert physician interviews, and an advisory board consisting of patients with PKU. Qualitative interviews combining concept elicitation/cognitive interviews were conducted with patients with classic PKU aged at least 15 years old. A separate sample of 20 patients with PKU completed the draft PKU-SSIS in a paper survey format, to enable preliminary assessment of any floor and ceiling effects.

Results

Patient interviews elicited four key symptom themes: neurocognitive function, emotional and behavioral, physical functioning, and physical health. Four impact themes were also identified: social function, physical health, emotions, and level of independence. No floor or ceiling effects were identified.

Conclusion

The final instrument included 22 items, covering three symptom domains (1. emotional, mood, and psychological; 2. (neuro)cognitive, executive, and intellectual function; and 3. physical health), and four impact domains (1. social relations, 2. level of independence, 3. general well-being, and 4. self-care). The PKU-SSIS will help to address an important gap in the evaluation of existing and future treatments for PKU.

Project "Backtoclinic I": An overview on the state of care of adult PKU patients in Austria

BACKGROUND

High rates of lost to follow-up (LTFU) adult patients are a major concern in the long-term management of phenylketonuria (PKU). To address this issue, we designed the project "Backtoclinic" with the purpose of identifying LTFU adult PKU patients in Austria as a first step to reestablish appropriate treatment.

SUBJECTS AND METHODS

Individuals born between 1966 and 1999 and diagnosed with PKU through the National Austrian Newborn Screening Program (NANSP) were identified using the NANSP's database. Follow-up data were collected in the Austrian metabolic centers (Medical University of Vienna, Graz, Innsbruck and Salzburg). Patients with no contact to any of these centers within the previous two years were classified as LTFU. Epidemiological characteristics of the whole study population as well as of LTFU- and currently in follow-up patients were analyzed.

RESULTS

Between 1966 and 1999, 281 individuals were diagnosed with PKU through the NANSP. Two patients died in their first year of life and were excluded from the analysis. Of the remaining 279 patients (mean age ± SD: 36.7 ± 9.1 y, 42.7% females), 177 (63.4%) are currently LTFU. The rate of LTFU patients is higher in men than in women (68.1% vs 57.5%), and markedly increases with age in both sexes. The gender gap is greatest in young adults (52.6% vs. 25.0% in the age range 20.0-24.9 y) and declines with age (94.4% vs. 80.0% in the age range > 45.0 y).

CONCLUSIONS

We found an alarming rate of 63.4% of LTFU adult PKU patients in Austria, and observed a gender gap in the PKU state of care. Our findings illustrate the urgent need for the metabolic community to identify LTFU adult PKU patients and to develop strategies to reestablish appropriate treatment for men and women with PKU.