Subtypes of avoidant/restrictive food intake disorder in children and adolescents: a latent class analysis.

Background: The Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5) describes three primary avoidant/restrictive food intake disorder (ARFID) subtypes including sensory sensitivity, lack of interest in food or eating, and fear of aversive consequences. Studies exploring these subtypes have yielded varying results. We used latent class analysis (LCA) based on the psychopathology of ARFID in a sample of children and adolescents to empirically identify classes. Methods: We carried out a surveillance study of ARFID in collaboration with the British Paediatric Surveillance Unit (BPSU) and the Child and Adolescent Psychiatry Surveillance System (CAPSS) in the United Kingdom and the Republic of Ireland from 1st of March 2021 to 31st of March 2022. Paediatricians and child and adolescent psychiatrists were contacted monthly to report newly diagnosed cases of ARFID electronically and complete a detailed clinical questionnaire. Cases aged 5-18 years were included. LCA was performed specifying 1-6 classes and likelihood-based tests for model selection. The Bayesian Information Criterion (BIC), the Akaike Information Criterion (AIC) and the Sample-Size Adjusted BIC were used to determine the most parsimonious model. Analysis of variance (ANOVA) and χ2 tests were used to compare the characteristics of the identified classes. A multinomial logistic regression (MLR) was performed to investigate predicting factors for the latent classes. Findings: We identified 319 children and adolescents with ARFID. LCA revealed four distinct classes which were labelled as Fear subtype, Lack of Interest subtype, Sensory subtype, and Combined subtype. The probability of being classified as these were 7.2% (n = 23), 25.1% (n = 80), 29.5% (n = 94) and 38.2% (n = 122), respectively. Age at diagnosis, sex, weight loss, distress associated with eating, and autism spectrum disorder diagnosis were identified as predictors of class membership. Interpretation: LCA identified four different classes in a sample of children and adolescents with ARFID. The Combined Subtype, a mixed presentation was the most common. The other three classes resembled the subtypes described in the literature. Clinicians should be aware of these different presentations of ARFID as they may benefit from different clinical interventions. Funding: This study was funded by the Former EMS Ltd (charity number 1098725, registered October 9th 2017).

Fetal alcohol syndrome in the UK.

OBJECTIVE: To determine the incidence of fetal alcohol syndrome (FAS) in the UK in children aged 0-16 years. DESIGN: Active surveillance was undertaken through the British Paediatric Surveillance Unit between October 2018 and October 2019 inclusive. Data were collected from reporting clinicians using standardised questionnaires. PATIENTS: Children aged 0-16 years in the UK and Ireland with a diagnosis of FAS seen in the previous month. This study did not include children with fetal alcohol spectrum disorder. MAIN OUTCOME MEASURES: Demographic details (including age and ethnicity), details of exposure, growth parameters, neurological and cognitive diagnoses, and service usage. RESULTS: 148 notifications were received. After exclusions and withdrawals, there were 10 confirmed and 37 probable cases (analysed together). Just 24 of these children were newly diagnosed with FAS during the surveillance period, giving an estimated incidence rate of 3.4/100 000 live births (95% CI 2.2 to 5.0); their median age at diagnosis was just over 5 years and they were diagnosed between 3 months and 14 years 3 months of age. CONCLUSIONS: The estimated incidence rate of FAS is lower than reported by similar studies and there was a wide variation in the age that cases were diagnosed. This, combined with the fact that many cases were notified and then withdrawn or excluded, suggests that in the UK there is a lack of consistency and certainty in diagnosing FAS. The study findings strongly support the need to educate key professionals involved in the care of infants and children at risk of FAS.

Neonatal stroke surveillance study protocol in the United Kingdom and Republic of Ireland.

Neonatal stroke is a devastating condition that causes brain injury in babies and often leads to lifelong neurological impairment. Recent prospective population studies of neonatal stroke are lacking. Neonatal strokes are different from those in older children and adults. A better understanding of its aetiology, current management, and outcomes could reduce the burden of this rare condition. The study aims to explore the incidence and 2 year outcomes of neonatal stroke across an entire population in the UK and Republic of Ireland. This is an active national surveillance study using a purpose-built integrated case notification-data collection online platform. Over a 13 month period, with a potential 6 month extension, clinicians will notify neonatal stroke cases presenting in the first 90 days of life electronically via the online platform monthly. Clinicians will complete a primary questionnaire via the platform detailing clinical information, including neuroimaging, for analysis and classification. An outcome questionnaire will be sent at 2 years of age via the platform. Appropriate ethics and regulatory approvals have been received. The neonatal stroke study represents the first multinational population surveillance study delivered via a purpose-built integrated case notification-data collection online platform and data safe haven, overcoming the challenges of setting up the study.

Key socio-demographic characteristics of children and adolescents with gender dysphoria: A British Isles surveillance study.

The present research used linked surveillance systems (British Paediatric Surveillance Unit; and the Child and Adolescent Psychiatry Surveillance System) over a 19 month period (1 November 2011-31 May 2013) to notify of young people (4-15.9 years) presenting to secondary care (paediatrics or child and adolescent mental health services) or specialist gender services with features of gender dysphoria (GD). A questionnaire about socio-demographic, mental health, and GD features was completed. Presence of GD was then assessed by experts in the field using then-current criteria (DSM-IV-TR). Incidence across the British Isles was 0.41-12.23 per 100,000. 230 confirmed cases of GD were noted; the majority were white (94%), aged ≥12 years (75.3%), and were assigned female at birth (57.8%). Assigned males presented most commonly in pre-adolescence (63.2%), and assigned females in adolescence (64.7%). Median age-of-onset of experiencing GD was 9.5 years (IQR 5-12); the majority reported long-standing features (2-5 years in 36.1%, ≥5 years in 26.5%). Only 82.5% attended mainstream school. Bullying was reported in 47.4%, previous self-harm in 35.2%, neurodiversity in 16%, and 51.5% had ≥1 mental health condition. These findings suggest GD is rare within this age group but that monitoring wellbeing and ensuring support for co-occurring difficulties is vital.

Paediatric multisystem inflammatory syndrome temporally associated with SARS-CoV-2 (PIMS-TS): Prospective, national surveillance, United Kingdom and Ireland, 2020.

BACKGROUND: Paediatric Multisystem Inflammatory Syndrome temporally associated with SARS-CoV-2 (PIMS-TS), first identified in April 2020, shares features of both Kawasaki disease (KD) and toxic shock syndrome (TSS). The surveillance describes the epidemiology and clinical characteristics of PIMS-TS in the United Kingdom and Ireland. METHODS: Public Health England initiated prospective national surveillance of PIMS-TS through the British Paediatric Surveillance Unit. Paediatricians were contacted monthly to report PIMS-TS, KD and TSS cases electronically and complete a detailed clinical questionnaire. Cases with symptom onset between 01 March and 15 June 2020 were included. FINDINGS: There were 216 cases with features of PIMS-TS alone, 13 with features of both PIMS-TS and KD, 28 with features of PIMS-TS and TSS and 11 with features of PIMS-TS, KD and TSS, with differences in age, ethnicity, clinical presentation and disease severity between the phenotypic groups. There was a strong geographical and temporal association between SARS-CoV-2 infection rates and PIMS-TS cases. Of those tested, 14.8% (39/264) children had a positive SARS-CoV-2 RT-PCR, and 63.6% (75/118) were positive for SARS-CoV-2 antibodies. In total 44·0% (118/268) required intensive care, which was more common in cases with a TSS phenotype. Three of five children with cardiac arrest had TSS phenotype. Three children (1·1%) died. INTERPRETATION: The strong association between SARS-CoV-2 infection and PIMS-TS emphasises the importance of maintaining low community infection rates to reduce the risk of this rare but severe complication in children and adolescents. Close follow-up will be important to monitor long-term complications in children with PIMS-TS. FUNDING: PHE.

Involvement of community paediatricians in the care of children and young people with mental health difficulties in the UK: implications for case ascertainment by child and adolescent psychiatric, and paediatric surveillance systems.

Objective: To ascertain the extent to which community paediatricians are involved in the care of children with mental health conditions in order to determine which difficulties are appropriate for single or joint surveillance by the British Paediatric Surveillance Unit (BPSU) and Child and Adolescent Psychiatry Surveillance System (CAPSS). Design: An online survey of the 1120 members of the British Association of Community Child Health (BACCH) working in 169 Community Child Health (CCH) services in the UK. Results: A total of 245 community paediatricians responded to the survey. This represents 22% of members of BACCH but likely to have covered many of the 169 CCH units because participants could respond on behalf of other members in their unit. The survey showed that children and young people (CYP) with neurodevelopmental conditions presented more frequently to paediatrics than to Child and Adolescent Mental Health Services (CAMHS). In addition, a sizeable proportion of CYP with emotional difficulties presented to paediatricians (eg, 29.5% for anxiety/obsessive compulsive disorder (OCD), and 12.8% for depression)-mainly due to difficulty with accessing CAMHS. More than half of the community paediatricians are involved in the care of CYP with anxiety and OCD, while 32.3% are involved in the care of those with depression. Conclusion: There is significant involvement of community paediatricians in the care of CYP with mental health conditions. Involvement is highest for neurodevelopmental conditions, but also significant for CYP with emotional difficulties. The implication of the findings for surveillance case ascertainment is that joint BPSU and CAPSS is recommended for surveillance studies of neurodevelopmental conditions. However, for emotional disorders, single or joint surveillance should be made based on the specific research question and the relative trade-offs between case ascertainment, and the additional cost and reporting burden of joint surveillance. Single CAPSS studies remain appropriate for psychosis and bipolar disorder.

Epidemiological surveillance study of female genital mutilation in the UK.

OBJECTIVES: Describe cases of female genital mutilation (FGM) presenting to consultant paediatricians and sexual assault referral centres (SARCs), including demographics, medical symptoms, examination findings and outcome. DESIGN: The well-established epidemiological surveillance study performed through the British Paediatric Surveillance Unit included FGM on the monthly returns. SETTING: All consultant paediatricians and relevant SARC leads across the UK and Ireland. PATIENTS: Under 16 years old with FGM. INTERVENTIONS: Data on cases from November 2015 to November 2017 and 12 months later meeting the case definition of FGM. MAIN OUTCOME MEASURES: Returns included 146 cases, 103 (71%) had confirmed FGM and 43 (29%) did not meet the case definition. There were none from Northern Ireland. RESULTS: The mean reported age was 3 years. Using the WHO classification of FGM, 58% (n=60) had either type 1 or type 2, 8% (n=8) had type 3 and 21% (n=22) had type 4. 13% (n=13) of the cases were not classified and none had piercings or labiaplasty. The majority, 70% had FGM performed in Africa with others from Europe, Middle East and South-East Asia. There were few physical and mental health symptoms. Only one case resulted in a successful prosecution. CONCLUSIONS: There were low numbers of children presenting with FGM and in the 2 years there was only one prosecution. The findings may be consistent with attitude changes in FGM practising communities and those at risk should be protected and supported by culturally competent national policies.

Nutritional rickets under 16 years: UK surveillance results.

OBJECTIVE: The UK national incidence of nutritional rickets is unknown. We aimed to describe the incidence, presentation and clinical management of children under 16 years with nutritional rickets in the UK presenting to secondary care. METHODS: Prospective data were collected monthly between March 2015 and March 2017 from 3500 consultant paediatricians using British Paediatric Surveillance Unit methodology. Clinicians completed online clinical questionnaires for cases fitting the surveillance case definition. RESULTS: 125 cases met the case definition, an annual incidence of 0.48 (95% CI 0.37 to 0.62) per 100 000 children under 16 years. 116 children were under 5 years (annual incidence of 1.39 (95% CI 1.05 to 1.81) per 100 000. Boys (70%) were significantly more affected than girls (30%) (OR 2.17, 95% CI 1.25 to 3.78). The majority were of Black (43%) or South Asian (38%) ethnicity. 77.6% of children were not taking vitamin D supplements despite being eligible. Complications included delayed gross motor development (26.4%), fractures (9.6%), hypocalcaemic seizures (8%) and dilated cardiomyopathy (3%). Two children died (1.6%). In eight cases, rickets was confirmed radiologically and biochemically [raised serum alkaline phosphatase (ALP) and parathyroid hormone (PTH) levels ] but were excluded from the incidence analysis for not meeting the case definition of 25-hydroxyvitamin D of <25 nmol/L. CONCLUSION: The incidence of nutritional rickets in the UK is lower than expected. Serious complications and unexpected deaths, particularly in Black and South Asian children under 5 years, occurred. Both vitamin D deficiency and dietary calcium deficiency are role players in pathogenesis. Uptake of vitamin D supplementation remains low.

Case ascertainment in active paediatric surveillance systems: a report from the British Paediatric Surveillance Unit Ascertainment Group.

The British Paediatric Surveillance Unit (BPSU) conducts surveillance of rare paediatric conditions using active, or prospective, case finding. The reliability of estimates of incidence, which is the primary outcome of public health importance, depends on ascertainment being as near complete as possible. This paper reviews evidence of the completeness of ascertainment in recent surveillance studies run through the BPSU. Ascertainment varied between 49% and 94% depending on the study. These are upper estimates. This was the basis of a discussion on barriers and facilitators of ascertainment which we have separated into factors related to the condition, factors related to the study methods, factors related to the study team and factors related to the surveillance system infrastructure. This leads to a series of recommendations to ensure continuing high levels of ascertainment in active surveillance studies.

Transition between child and adult services for young people with attention-deficit hyperactivity disorder (ADHD): findings from a British national surveillance study.

BACKGROUND: Optimal transition from child to adult services involves continuity, joint care, planning meetings and information transfer; commissioners and service providers therefore need data on how many people require that service. Although attention-deficit hyperactivity disorder (ADHD) frequently persists into adulthood, evidence is limited on these transitions. AIMS: To estimate the national incidence of young people taking medication for ADHD that require and complete transition, and to describe the proportion that experienced optimal transition. METHOD: Surveillance over 12 months using the British Paediatric Surveillance Unit and Child and Adolescent Psychiatry Surveillance System, including baseline notification and follow-up questionnaires. RESULTS: Questionnaire response was 79% at baseline and 82% at follow-up. For those aged 17-19, incident rate (range adjusted for non-response) of transition need was 202-511 per 100 000 people aged 17-19 per year, with successful transition of 38-96 per 100 000 people aged 17-19 per year. Eligible young people with ADHD were mostly male (77%) with a comorbid condition (62%). Half were referred to specialist adult ADHD and 25% to general adult mental health services; 64% had referral accepted but only 22% attended a first appointment. Only 6% met optimal transition criteria. CONCLUSIONS: As inclusion criteria required participants to be on medication, these estimates represent the lower limit of the transition need. Two critical points were apparent: referral acceptance and first appointment attendance. The low rate of successful transition and limited guideline adherence indicates significant need for commissioners and service providers to improve service transition experiences.

How to measure the need for transition to adult services among young people with Attention Deficit Hyperactivity Disorder (ADHD): a comparison of surveillance versus case note review methods.

BACKGROUND: Health services have not provided adequate support for young people with long term health conditions to transfer from child to adult services. National Institute of Health and Care (NICE) guidance on transition has been issued to address these gaps. However, data are often sparse about the number of young adults who might need to transition. Using Attention Deficit Hyperactivity Disorder (ADHD) as an exemplar, this study used an existing surveillance system and a case note review to capture the incidence of the transition process, and compared and contrasted the findings. METHODS: The Child and Adolescent Psychiatry Surveillance System (CAPSS) was used to estimate the incident transition of young people with Attention Deficit Hyperactivity Disorder (ADHD) from child to adult services. This involves consultant child and adolescent psychiatrists from the United Kingdom (UK) and Republic of Ireland (ROI) reporting relevant young people as they are seen in clinics. In parallel, a case note review was conducted using the Maudsley Biomedical Research Centre (BRC) Clinical Records Interactive Search (CRIS). The study period ran for twelve months with a nine month follow up to see how the transition proceeded. RESULTS: CRIS identified 76 cases in the study period, compared to 18 identified using surveillance via CAPSS. Methodological issues were experienced using both methods. Surveillance issues; eligibility criteria confusion, reporting errors, incomplete questionnaires, difficulties contacting clinicians, and surveillance systems do not cover non-doctors and psychiatrists who are not consultants. Case note review issues using CRIS included the need for researchers to interpret clinical notes, the availability and completeness of data in the notes, and data limited to the catchment of one particular mental health trust. CONCLUSIONS: Both methods demonstrate strengths and weaknesses; the combination of both methods in the absence of strong routinely collected data, allowed a more robust estimate of the level of need for service planning and commissioning.

Kawasaki disease: a prospective population survey in the UK and Ireland from 2013 to 2015.

OBJECTIVE: Kawasaki disease (KD) is an increasingly common vasculitis with risk of coronary artery aneurysms (CAAs). The last UK survey was in 1990, whereas current epidemiology, treatment patterns and complication rates are unknown. The aim of this study was to address this knowledge gap. METHODS: A British Paediatric Surveillance Unit survey in the UK and Ireland from 1 January 2013 to 28 February 2015 ascertained demographics, ethnicity, seasonal incidence, treatment and complication rates. RESULTS: 553 cases were notified: 389 had complete KD, 46 had atypical KD and 116 had incomplete KD; 2 were diagnosed at postmortem with an incidence of 4.55/100 000 children under 5 years, with a male to female ratio of 1.5:1 and a median age of 2.7 years (2.5 months-15 years). Presentation was highest in January and in rural areas. Most were white (64%), and Chinese and Japanese Asians were over-represented as were black African or African mixed-race children. 94% received intravenous immunoglobulin (IVIG). The overall CAA rate was 19%, and all-cardiac complications affected 28%. Those with CAA received IVIG later than in those without (median 10 days vs 7 days). Those under 1 year had fewer symptoms, but the highest CAA rate (39%). Overall 8 of 512 cases (1.6%) had giant CAA, and 4 of 86 cases (5%) under 1 year of age developed giant CAA. Mortality from KD was 0.36%. CONCLUSIONS: The UK and Ireland incidence of KD has increased and is more frequently seen in winter and rural areas. Delayed IVIG treatment is associated with CAA, suggesting earlier and adjunctive primary treatment might reduce complications to prevent CAA, particularly in the very young.

Treatment adherence and BMI reduction are key predictors of HbA1c 1 year after diagnosis of childhood type 2 diabetes in the United Kingdom.

BACKGROUND/OBJECTIVE: Type 2 Diabetes (T2DM) is increasing in childhood especially among females and South-Asians. Our objective was to report outcomes from a national cohort of children and adolescents with T2DM 1 year following diagnosis. METHODS: Clinician reported, 1-year follow-up of a cohort of children (<17 years) diagnosed with T2DM reported through the British Paediatric Surveillance Unit (BPSU) (April 2015-April 2016). RESULTS: One hundred (94%) of 106 baseline cases were available for review. Of these, five were lost to follow up and one had a revised diagnosis. Mean age at follow up was 15.3 years. Median BMI standard deviation scores (SDS) was 2.81 with a decrease of 0.13 SDS over a year. HbA1c <48 mmol/mol (UK target) was achieved in 38.8%. logHbA1c was predicted by clinician reported compliance and attendance concerns (ß = 0.12, P = <0.0001) and change in body mass index (BMI) SDS at 1-year (ß = 0.13, P=0.007). In over 50%, clinicians reported issues with compliance and attendance. Mean clinic attendance was 75%. Metformin was the most frequently used treatment at baseline (77%) and follow-up (87%). Microalbuminuria prevalence at 1-year was 16.4% compared to 4.2% at baseline and was associated with a higher HbA1c compared to those without microalbuminuria (60 vs 49 mmol/mol, P = 0.03). CONCLUSIONS: Adherence to treatment and a reduction in BMI appear key to better outcomes a year after T2DM diagnosis. Retention and clinic attendance are concerning. The prevalence of microalbuminuria has increased 4-fold in the year following diagnosis and was associated with higher HbA1c.

Classification of childhood onset eating disorders: A latent class analysis.

This study tested the hypothesis that latent class analysis (LCA) would successfully classify eating disorder (ED) symptoms in children into categories that mapped onto DSM-5 diagnoses and that these categories would be consistent across countries. Childhood onset ED cases were ascertained through prospective active surveillance by the Australian Paediatric Surveillance Unit, the Canadian Paediatric Surveillance Program, and the British Paediatric Surveillance Unit for 36, 24, and 14 months, respectively. Pediatricians and child psychiatrists reported symptoms of any child aged ≤ 12 years with a newly diagnosed restrictive ED. Descriptive analyses and LCA were performed separately for all three countries and compared. Four hundred and thirty-six children were included in the analysis (Australia n = 70; Canada n = 160; United Kingdom n = 206). In each country, LCA revealed two distinct clusters, both of which presented with food avoidance. Cluster 1 (75%, 71%, 66% of the Australian, Canadian, and United Kingdom populations, respectively) presented with symptoms of greater weight preoccupation, fear of being fat, body image distortion, and over exercising, while Cluster 2 did not (all p < .05). Cluster 1 was older, had greater mean weight loss and was more likely to have been admitted to an inpatient unit and have unstable vital signs (all p < .01). Cluster 2 was more likely to present with a comorbid psychiatric disorder (p < .01). Clusters 1 and 2 closely resembled the DSM-5 criteria for anorexia nervosa and avoidant/restrictive food intake disorder, respectively. Symptomatology and distribution were remarkably similar among countries, which lends support to two separate and distinct restrictive ED diagnoses.

Incidence and Clinical Associations of Childhood Acute Pancreatitis.

OBJECTIVES: To establish the UK incidence and clinical associations of acute pancreatitis (AP) in children aged 0 to 14 years. METHODS: Monthly surveillance of new cases of AP in children under 15 years of age through the British Pediatric Surveillance Unit conducted from April 2013 to April 2014 (inclusive) followed by 1-year administrative follow-up for all valid cases. RESULTS: Ninety-four cases (48 boys) fulfilled the diagnostic criteria. The median age at diagnosis was 11.2 years (range 1.3-14.9). White children accounted for 61% of the cases compared with 28% from Asian and 5% from African ethnicities. Pakistani children accounted for 18 of 26 (69%) Asian patients and 19% of the total cohort. The incidence of AP in children in the United Kingdom was 0.78 per 100 000/year (95% confidence interval [CI] 0.62-0.96). The incidence in Pakistani children (4.55; 95% CI 2.60-7.39) was sevenfold greater than white children (0.63; 95% CI 0.47-0.83). Of the 94 cases, 35 (37%) were idiopathic; other associations were: drug therapy, 18 (19%); gallstones, 12 (13%); hereditary, 7 (7%); organic acidemias, 7 (7%); anatomic anomalies, 5 (5%); viral infections, 3 (3%); systemic diseases, 2 (2%); and trauma 1 (1%). The most common drug associations were asparaginase (28%), azathioprine (17%), and sodium valproate (17%). CONCLUSIONS: Although still relatively uncommon in the United Kingdom, on average there is >1 case of childhood AP diagnosed every week. The associations of AP have changed significantly since the 1970-80s. Overrepresentation of Pakistani children is worthy of further investigation.

Medical instability and growth of children and adolescents with early onset eating disorders.

OBJECTIVE: Little is known about the physical burden of early onset eating disorders (EOEDs). Most published data on physical instability and growth in malnutrition come from specialist centres, or from the developing world where aetiology differs. The authors present data on physical status at presentation from population-based surveillance systems in the UK and Ireland. DESIGN: Prospective surveillance study. PARTICIPANTS: All suspected cases of EOED in children under 13 years of age reported by paediatricians and psychiatrists via the British Paediatric Surveillance System (BPSU) and Child and Adolescent Psychiatric Surveillance System (CAPSS) in the UK and Ireland from March 2005 to May 2006 (15 months). RESULTS: 208 cases were identified (24% reported by paediatricians). Median age was 11.8 years (IQR 1.74). 171 (82%) were female (78% premenarcheal and 60% prepubertal). 74% of males were prepubertal. 35% of cases had medical instability at presentation (60% bradycardia, 54% hypotension, 34% dehydration, 26% hypothermia). 52% of cases required admission at diagnosis (73% to a paediatric ward). 41% of cases with medical instability were not underweight, that is, they had body mass index (BMI) z-scores above -2.0 (2nd centile). Sensitivities for identifying medical instability with BMI z-score <-3 or 70% median BMI were 31% and 15%, respectively. Menarcheal status did not predict risk of medical instability. CONCLUSIONS: EOEDs present with severe levels of physical instability and frequently to paediatricians. As anthropological indices alone are poor markers for medical instability, clinical assessment is essential. Doctors providing care for children have a central role in both the recognition and management of EOEDs.

Childhood hemolytic uremic syndrome, United Kingdom and Ireland.

We conducted prospective surveillance of childhood hemolytic uremic syndrome (HUS) from 1997 to 2001 to describe disease incidence and clinical, epidemiologic and microbiologic characteristics. We compared our findings, where possible, with those of a previous study conducted from 1985 to 1988. The average annual incidence of HUS for the United Kingdom and Ireland (0.71/100,000) was unchanged from 1985 to 1988. The overall early mortality had halved, but the reduction in mortality was almost entirely accounted for by improved outcome in patients with diarrhea-associated HUS. The principal infective cause of diarrhea-associated HUS was Shiga toxin-producing Escherichia coli O157 (STEC O157), although in the 1997-2001 survey STEC O157 phage type (PT) 21/28 had replaced STEC O157 PT2 as the predominant PT. The risk of developing diarrhea-associated HUS was significantly higher in children infected with STEC O157 PT 2 and PT 21/28 compared with other PTs. Hypertension as a complication of HUS was greatly reduced in patients with diarrhea-associated HUS.