The diagnostic odyssey in children and adolescents with X-linked hypophosphataemia: population-based, case-control study.

CONTEXT: X-linked hypophosphataemia (XLH) is a rare genetic disorder causing renal phosphate wasting, which predicates musculoskeletal manifestations such as rickets. Diagnosis is often delayed. OBJECTIVE: To explore the recording of clinical features, and the diagnostic odyssey of children and adolescents with XLH in primary care electronic healthcare records (EHR) in the United Kingdom. METHODS: Using the Optimum Patient Care Research Database, individuals aged 20 years or younger after 1st Jan 2000 at date of recorded XLH diagnosis were identified using SNOMED/Read codes, and age-matched to 100 controls. Recording of XLH-related clinical features was summarised, then compared between cases and controls using Chi-squared or Fisher's exact tests. RESULTS: 261 XLH cases were identified; 99 met inclusion criteria. Of these, 84/99 had at least 1 XLH-related clinical feature recorded in their primary care EHR. Clinical codes for rickets, genu varum and low phosphate were recorded prior to XLH diagnosis in under 20% of cases (median of 1, 1, and 3 years prior, respectively). Rickets, genu varum, low phosphate, nephrocalcinosis and growth delay were significantly more likely to be recorded in cases. CONCLUSION: This characterisation of the EHR phenotypes of children and adolescents with XLH may inform future case-finding approaches to expedite diagnosis in primary care.