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Introduction
Overview
Acute rheumatic fever
Rheumatic heart disease
Secondary prophylaxis

Introduction

In the Northern Territory, the rates of acute rheumatic fever (ARF) and rheumatic heart disease (RHD) for Aboriginal and Torres Strait Islander people are among the highest in the world, and the rates are much higher than for non-Indigenous Territorians.

In the Northern Territory, the collection of ARF and RHD notifications is funded by the Australian Government Department of Health. Definite ARF has been a notifiable disease in the Northern Territory since 1996, and the register and RHD control program were established in 1997. Although RHD only became notifiable in the Northern Territory in 2019, diagnoses had been recorded on the register for many years.

Overview

At 31 December 2020, there were 3,805 people living with a diagnosis of ARF and/or RHD in the Northern Territory. This represents 42% of the total 9,158 people recorded across all 5 jurisdictional registers. Of these 3,805 people in the Northern Territory, 1,456 people (38%) had only ARF recorded on the register, 962 people (25%) had only RHD recorded and 1,387 people (36%) had both ARF and RHD recorded (Supplementary Overview Table 1).

Region of management

For each person recorded on a register, the region of management is recorded. This is the area where the patient was most recently reported to receive the majority of the primary health care for their ARF or RHD. The region of management may differ from the person’s region of diagnosis and the notifying jurisdiction. Each state or territory defines regions uniquely, based on its own specific health services boundaries. There are 33 regions spread over Queensland, Western Australia, South Australia, and the Northern Territory. NSW is considered as a whole. Regions do not cross state and territory boundaries.

Rural Darwin was the region in the Northern Territory with the highest rate of ARF and/or RHD management (Figure 2.1) (Supplementary Overview Table 4).

Figure 2.1: ARF and/or RHD diagnoses among Indigenous Australians in the Northern Territory, by region of management, as at 31 December 2020. Urban Darwin had the lowest rate of cases managed and Rural Darwin had the highest rate of cases managed in the NT.

Acute rheumatic fever

All Australians

In 2016–2020 in the Northern Territory:

  • 1,331 diagnoses of ARF were recorded in 1,191 people (108 per 100,000 population over the 5 years combined) (Supplementary ARF tables 1 and 2)
  • the number and rate of ARF diagnoses increased from 233 (95 per 100,000 population) in 2016 to 287 (117 per 100,000 population) in 2019. There was a decrease in cases in 2020 with 255 cases (104 per 100,000 population) (Figure 3.1) (Supplementary ARF Table 2)

Figure 3.1: ARF notifications among all Australians in the Northern Territory, by year, 2016–2020. The rate increased from 2016 to 2019 with a slight decrease in 2020.

  • the most common age at diagnosis was 5–14, with 585 diagnoses (338 per 100,000 population). Females accounted for 57% of diagnoses (Figure 3.2) (Supplementary ARF Table 3a)

Figure 3.2: ARF notifications among all Australians in the Northern Territory, by sex and age group, 2016–2020. Females had a higher rate than males in all ages except 5-14. The highest rate of ARF notifications was among those aged 5-14 years.

Indigenous Australians

In 2016–2020 in the Northern Territory:

  • 1,310 ARF episodes were diagnosed among Aboriginal and Torres Strait Islander people, a rate of 344 per 100,000 population (Supplementary ARF Table 2)
  • the diagnosis rate among Indigenous Australians increased between 2016 and 2019—from 306 to 372 per 100,000 population (228 to 286 diagnoses, respectively)—but then dipped to 322 per 100,000 population (250 diagnoses) in 2020 (Figure 3.3) (Supplementary ARF Table 2)

Figure 3.3: ARF notifications among Indigenous Australians in the Northern Territory, by year, 2016–2020. The rate increased from 2016 to 2019 with a slight decrease in 2020.

  • the highest rate of diagnosis among Indigenous Australians was among those aged 5–14, accounting for 44% of all diagnoses (783 per 100,000 population, or 577 diagnoses). Females accounted for 57% of diagnoses (750 diagnoses) (Figure 3.4) (Supplementary ARF Table 3b)

Figure 3.4: ARF notifications among Indigenous Australians in the Northern Territory, by sex and age group, 2016–2020. For Indigenous Australians, females had a higher rate than males in all ages except 5-14. The highest rate of ARF notifications was among those aged 5-14 years.

  • there were 406 recurrent ARF episodes recorded among Indigenous Australians (Supplementary ARF Table 7)
  • urban Alice Springs had the highest incidence of ARF (Figure 3.5) (Supplementary ARF Table 4)

Figure 3.5: ARF diagnoses among Indigenous Australians in the Northern Territory, by region of diagnoses, 2016–2020. Urban Darwin had the lowest rate of ARF notifications in the NT and Urban Alice Springs had the highest rate in the NT.

Rheumatic heart disease

Prevalence

At 31 December 2020, 2,305 people living with RHD were recorded on the Northern Territory register (Supplementary RHD Table 1).

Incidence

In 2016–2020 in the Northern Territory:

  • there were 576 reports of new RHD diagnoses (47 per 100,000 population) with no clear trend in annual diagnosis rates, which varied from 33 to 58 diagnoses per 100,000 population (Figure 4.1) (Supplementary RHD Table 4) 

Figure 4.1: New RHD diagnoses, all Australians in the Northern Territory, by year, 2016–2020. There was no clear annual trend.

  • 557 new RHD diagnoses among Indigenous Australians were reported to the jurisdictional register (146 per 100,000 population) (Supplementary RHD Table 4)
  • the annual rate has fluctuated between 101 and 185 per 100,000 population, with no clear trend (Figure 4.2) (Supplementary RHD Table 4)

Figure 4.2: New RHD diagnoses, Indigenous Australians in the Northern Territory, by year, 2016–2020. There was no clear annual trend.

  • new RHD diagnoses were more common among Indigenous females than males (197 and 98 diagnoses per 100,000 population, respectively) (Figure 4.3) (Supplementary RHD Table 5)
  • 60% of new diagnoses were among Indigenous Australians aged under 25 (333 diagnoses) (Supplementary RHD Table 5)
  • 61% of people diagnosed with RHD had mild disease at diagnosis, 30% had moderate disease and 9.5% had severe disease (Supplementary RHD Table 6).

Figure 4.3: New RHD diagnoses, Indigenous Australians in the Northern Territory, by age group and sex, 2016–2020. New RHD among Indigenous Australians was highest in those 15-24. The rate for Indigenous females was higher than Indigenous males for every age group.

Indigenous Australians with no documented previous ARF episode

RHD occurs only in someone who has had ARF, but some people with RHD have no recorded previous ARF episode on state and territory registers. ARF might not be notified to a register for various reasons, such as being diagnosed before the relevant register began; being diagnosed prior to the condition being notifiable; the person being in a jurisdiction that does not have a register; or the episode never being diagnosed.

Among Indigenous Australians in the Northern Territory with a new RHD diagnosis in 2016–2020, 445 (80%) did not have a previous ARF episode recorded on the registers. Of these:

  • females were more likely than males to have no recorded history of ARF (82% compared with 75%)
  • there was no clear relationship between age and the proportion of people who had no previous ARF recorded
  • there was no clear annual trend (Supplementary RHD Table 8).

Heart surgery for RHD

In 2016–2020 in the Northern Territory, 182 people underwent 190 RHD surgical events. Most of these people were Indigenous Australians, comprising 95% (173) of patients and 95% (180) of events (Supplementary RHD Table 9). Most surgical events among Indigenous Australians occurred among those aged 25–34 (57 surgical events, 32%) followed by those aged 45 and over (37 surgical events, 21%) (Figure 4.4) (Supplementary RHD Table 11).

Figure 4.4: Surgical events among Indigenous Australians with RHD in the Northern Territory, by age group, 2016–2020. Most surgical events took place in people 25-34.

Secondary prophylaxis

Delivery of secondary prophylaxis

In 2020, 2,320 people in the Northern Territory were prescribed a treatment regimen to prevent recurrences of ARF, and progression to RHD, involving regular intramuscular injections of BPG every 21 or 28 days. Of these, 2,282 were Indigenous Australians (Supplementary Secondary Prophylaxis Table 1).

In 2020, among Indigenous Australians in the Northern Territory prescribed 3- or 4-weekly BPG:

  • 20% (454 people) received 100% or more of their prescribed doses
  • 26% (597) received 80% to 99% of their prescribed doses
  • 27% (626) received 50% to 79% of their prescribed doses
  • 27% (605) received less than 50% of their prescribed doses, including 142 people who received no doses (Supplementary Secondary Prophylaxis Table 1)
  • females had higher adherence than males, with 48% receiving at least 80% of doses (compared with 43% for males) (Figure 5.1) (Supplementary Secondary Prophylaxis Table 2)

Figure 5.1: Proportion of doses received by Indigenous Australians in the Northern Territory with ARF and/or RHD on a BPG regime, by sex, 2020. Females and males had similar per cents for people with more than 80% of doses delivered. Females had a higher per cent of people with 50-79% delivered.

  • delivery was highest among people aged 0–14, with 59% receiving at least 80% of doses (Figure 5.2) (Supplementary Secondary Prophylaxis Table 3).

Figure 5.2: Proportion of doses received by Indigenous Australians with ARF and/or RHD in the Northern Territory on a BPG regime, by age group, 2020. People 45-64 had a higher per cent of people who received 100+% of their doses. Those aged 5-14 had the highest per cent of people receiving 80+% of doses. Those under 5 and those 65 and over had fewer cases, making per cent of cases delivered less reliable.

Time trend

The proportion of Indigenous Australians receiving at least 80% of their prescribed doses increased from 46% in 2016 to 49% in 2019, before dropping to 46% in 2020. In 2020, 6% of people did not receive any of their prescribed doses. The decrease in those receiving at least 80% of their prescribed doses could be due to the impacts of COVID-19 on health services and health service use (Figure 5.3) (Supplementary Secondary Prophylaxis Table 4).

Figure 5.3: Proportion of doses received by Indigenous Australians with ARF and/or RHD in the Northern Territory on a BPG regime, by year, 2016–2020. The per cent of patients receiving 100+% of their doses increased each year until 2019 when it dropped. This is likely due to impacts of the COVID-19 pandemic on healthcare services.

ARF recurrence rate among people on BPG

In 2020, among Indigenous Australians prescribed BPG in the Northern Territory, there were 76 ARF recurrences and a rate of 3.6 recurrences per 100 patient-years (Supplementary Secondary Prophylaxis Table 5). The rate of recurrence per 100 patient-years generally decreased with age, with the highest risk among those aged 5–14 (4.5) (Figure 5.4) (Supplementary Secondary Prophylaxis Table 5).

Figure 5.4: ARF recurrences per 100 patient-years, Indigenous Australians in the Northern Territory on a BPG regime, by age group, 2020. Those aged 5-14 had the highest recurrences per 100 patient-years. There were no recurrences in those under 5.

Between 2016 and 2020, the ARF recurrence rate per 100 patient-years among Indigenous Australians prescribed BPG decreased from 5.3 to 3.6 (Figure 5.5) (Supplementary Secondary Prophylaxis Table 6).

Figure 5.5: Rate of recurrence, Indigenous Australians with ARF and/or RHD in the Northern Territory on a BPG regime, by year, 2016–2020. The rate of recurrence decreased over time.