Dravet Prevalence in the UK Is Low, Healthcare Utilization for It Is High

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by Steve Bryson, PhD |

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The prevalence of Dravet syndrome in the U.K. is low, with most patients diagnosed before age 18, a large-scale healthcare database analysis showed.

The findings also showed that the use of anti-seizure medications and healthcare resources was high among those with Dravet.

This study provided valuable information on the burden of illness in patients with Dravet syndrome in the U.K., the researchers said.

The analysis was published in Seizure, in the study, “Prevalence and healthcare resource utilization of patients with Dravet syndrome: Retrospective linkage cohort study.”

Dravet syndrome is a rare childhood-onset type of epilepsy caused mainly by mutations in the SCN1A gene and marked by intellectual disability, coexisting medical conditions, and premature mortality. Despite treatment with anti-seizure medications (ASMs), disease management is poor, and patients utilize healthcare resources at a high rate.

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Due to updates in managing medical records in the U.K., large-scale healthcare data are now available from the Clinical Practice Research Datalink (CPRD), with primary and secondary healthcare data captured in electronic medical records.

Recently, a study using the CPRD improved the understanding about the prevalence of Lennox-Gastaut syndrome, another rare childhood-onset epilepsy, and how healthcare for it is utilized.

Researchers at Swansea University in the U.K. have now tapped the CPRD to examine the prevalence, usage of anti-seizure medications, healthcare utilization, and mortality of patients with Dravet syndrome.

“This is the first study to use large-scale healthcare data to determine UK prevalence and [healthcare utilization] for patients with [Dravet syndrome],” the research team wrote.

At the time of the study, the CPRD contained 13.7 million of de-identified electronic medical records collected between the beginning of January 1987 and the end of February 2019.

Examining the database revealed 32 people with confirmed Dravet syndrome and 22 with probable Dravet. The median age at diagnosis was higher for confirmed cases at 5.5 years (range 0–45) compared to probable cases at 1 year (range 0–40).

This difference in the age of diagnosis “likely reflects the delay in [Dravet syndrome] diagnosis after seizure onset in the affected child that may result from the evolving [Dravet syndrome] phenotype and diagnosis,” the researchers wrote.

The age at first epilepsy diagnosis — 1 year — was similar between patients with confirmed and probable Dravet. The median years of follow-up data were 2.6 for confirmed cases (range 0.1–18.3) and 11.0 for probable cases (range 1.5–25.2).

Among the 54 patients with confirmed or probable Dravet, 12 were lost to follow-up before 2017. Using data from the remaining 42 patients, of whom 28 were confirmed cases, the prevalence of Dravet in 2017 was 1.5 cases per 100,000 people. For confirmed patients, the prevalence was 1.1/100,000, and for probable, 0.6/100,000.

In 2017, most patients with Dravet were under the age of 18, including 22 of the 28 confirmed cases and eight of the 14 probable patients, which “may partially be explained by the impact of childhood mortality on adult prevalence,” the scientists wrote.

Other reasons for this difference may include misdiagnosing Dravet or the challenge of diagnosing adults who may no longer display typical seizures, they said. Patients may also have been diagnosed with treatment-resistant epilepsy before Dravet was widely recognized and routine genetic testing was introduced.

Before 2010, a confirmed Dravet diagnosis was rare, but peaked at 13 cases in 2013–14. This coincides with the introduction of diagnostic medical codes for Dravet and severe myoclonic epilepsy in infancy (SMEI), the previous name for Dravet, the scientists noted.

The first probable Dravet case was registered in 1989, while none were registered after SMEI and Dravet codes were introduced.

Anti-seizure medication usage was investigated for all 54 people. During the follow-up period, 10% or more of Dravet patients used 15 anti-seizure medications.

For confirmed cases, the most frequently prescribed anti-seizure medications were midazolam (88%), valproate, which is sold as Depacon in the U.S. and Epilim in the U.K. (81%), and clobazam, which is sold as Onfi (72%). Among probable Dravet cases, stiripentol, sold as Diacomit (91%), was the most frequently prescribed anti-seizure medication, followed by valproate (86%) and clobazam (86%).

The mean number of anti-seizure medications prescribed to confirmed cases, at 5.5 (range 1–12), was similar to that of probable cases, at 7.5 (range 3–15). About one anti-seizure medication was prescribed each year of follow-up.

Healthcare utilization was assessed for all 54 patients for primary care and 27 for secondary care, including 13 confirmed and 14 probable cases.

In primary care, consultation with a general practitioner (GP) was the most common contact, followed by GP home visits, then nurse consultations. Regardless of age, probable cases had slightly more primary care contact than confirmed Dravet cases.

In secondary care, outpatient visits were the most common type of healthcare used, which was similar between confirmed and probable cases, independent of age. This was followed by hospital admissions and emergency department visits.

Under age 12, probable Dravet cases had more total and epilepsy-related hospital admissions and emergency department visits than confirmed cases. These numbers were similar at 12 and older. Time in the hospital was similar between confirmed and probable Dravet younger than 12, but longer for probable cases 12 and older.

Although fewer than five deaths were reported, the exact number was not disclosed to protect against patients being identified.

“This study provides valuable information on the UK burden of illness in patients with [Dravet syndrome] and highlights the high [healthcare utilization] and ASM usage,” the team concluded. “UK prevalence of [Dravet syndrome] recorded in primary care was low. Most patients with [Dravet syndrome] were aged [less than] 18 years.”