ARF among Indigenous Australians

The age and sex distribution of ARF cases among Indigenous Australians follows the pattern described above for all Australians. Children aged 5–14 years have the highest rates of ARF diagnosis and constitute one-third of all cases (602 diagnoses).

More Indigenous females are diagnosed with ARF than Indigenous males, with 57% of reported Indigenous cases being in females (1,006 diagnoses). ARF rates in adults are generally higher among females than males, but in children the rates are higher in males.

Table 2: Number and rate of ARF diagnoses per 100,000 among Indigenous Australians by sex and age, 2013–2017

Age group (years)

Male number

Male rate (per  100,000)

Female number

Female rate (per 100,000)

Total number

Total rate (per 100,000)

0–4

32

25.5

30

25.1

62

25.3

5–14

478

203.1

424

185.9

902

194.6

15–24

151

70.6

274

134.2

425

101.6

25–44

104

37.6

256

90.9

360

64.5

45 +

5

2.6

22

10.3

27

6.7

Total

770

73.8

1,006

96.1

1,776

85.0

Notes:

  1. ARF diagnoses include all episode types and confirmation statuses. Refer to box 2 and 3 for more information.
  2. Rates are crude rates per 100,000 population

Source: AIHW analysis of National Rheumatic Heart Disease data collection.

ARF diagnoses by state and territory and region

Numbers and rates of ARF amongst Indigenous Australians during 2013–2017 were consistently highest in the Northern Territory. Fifty-three per cent (954) of all diagnoses were from NT.  

The rate generally increased over time in each jurisdiction, apart from in Western Australia, where there was no clear pattern. In the NT in 2017, 268 diagnoses were recorded, more than twice the number recorded in 2013 (127). The number of diagnoses made in QLD almost tripled over the period (from 43 to 124).

Table 3: Rate of ARF diagnoses per 100,000 among Indigenous Australians, by state and territory, 2013–2017

Year

Qld (per 100,000)

WA (per 100,000)

SA (per 100,000)

NT (per 100,000)

Total (per 100,000)

2013

21.7

80.5

25.7

178.6

63.5

2014

36.0

57.6

37.7

200.7

70.2

2015

32.7

63.7

22.1

241.2

75.4

2016

59.6

59.4

33.7

318.0

102.1

2017

56.8

75.2

40.1

354.1

110.9

Total rate

41.8

67.3

32.0

260.0

85.0

Notes:

  1. ARF diagnoses include all episode types and confirmation statuses. Refer to box 2 and 3 for more information.
  2. Rates are crude rates per 100,000 population

Source: AIHW analysis of National Rheumatic Heart Disease data collection.

For each ARF case, the RHD registers record the region where the patient receives the majority of their ARF health care. This region may be distinct from the region where diagnosis and GAS infection occurred.

The rate of ARF in each jurisdiction generally increased with remoteness. Over the period 2013–2017, the region with the highest rate of ARF notifications was Rural Darwin in the NT (249 diagnoses or 387 per 100,000). East Arnhem in the NT (212 diagnoses or 366 per 100,000) and the Kimberley in WA (180 diagnoses or 200 per 100,000) also had relatively high rates.

Figure 2: Rate of ARF diagnoses per 100,000 among Indigenous Australians by region of management, 2013–2017  

Notes:

  1. There are 33 regions across the 4 states and territories. Each state and territory define regions uniquely, based on their own specific health services boundaries.  
  2. Rates are crude rates per 100,000 population.
  3. ARF diagnoses include all episode types and confirmation statuses. Refer to box 2 and 3 for more information.
  4. No data are available for jurisdictions not included in the National Rheumatic Heart Disease data collection.
  5. For Queensland regions, the 2016 population estimates were used to calculate rates for 2016 and 2017.

Source: AIHW analysis of National Rheumatic Heart Disease data collection.

ARF among Indigenous Australians by diagnostic category

Box 2. ARF diagnostic categories (for first known episode)

(RHD Australia, 2012)

There is no specific diagnostic test for ARF. Instead, it is diagnosed based on medical history and a pattern of clinical features (‘manifestations’) as follows:

  • Definite ARF: 2 major or 1 major and 2 minor manifestations plus evidence of preceding GAS infection. Long–term preventive penicillin should commence.
  • Probable ARF: clinical presentation falls short by either one major or one minor manifestation, or the absence of streptococcal serology results, but where ARF is the most likely diagnosis. Long–term preventive penicillin should commence.
  • Possible ARF: Strong clinical suspicion of ARF, but insufficient signs and symptoms for diagnosis of definite or probable ARF. Preventive penicillin should commence, with a clinical review scheduled for 12 months later, to determine if it should continue long– term.

Nearly three-quarters of all ARF diagnoses among Indigenous Australians in 2013–2017, were for definite ARF (1,284 diagnoses, 72%). Probable diagnoses made up 17% (296 diagnoses) and 11% of diagnoses were possible (195 diagnoses).

Between 2013 and 2017, rates for definite or probable ARF increased from 59 per 100,000 (234 diagnoses) to 106 per 100,000 (424 diagnoses), in line with overall increases in ARF regardless of diagnostic category. However, the proportion of definite or probable ARF diagnoses decreased from 92% in 2013 to 88% in 2017, with a corresponding increase in possible diagnoses. Older Indigenous Australians were more likely to have a definite or probable ARF diagnosis and the patterns in diagnostic category were similar in males and females.

ARF diagnoses by recurrence status 

Box 3. ARF recurrence status definitions

  • First known episode: A reported ARF episode (definite, probable or possible) in an individual with no known past ARF or RHD.
  • Recurrence status: A reported ARF episode (definite, probable or possible) in an individual with known past ARF or RHD.

Both first known ARF episodes and recurrent episodes are preventable. After the first known ARF episode, adherence to secondary prophylaxis reduces the likelihood of a recurrence.

In 2013–2017, three-quarters of ARF diagnoses (74%, 1,316 diagnoses) were recorded as the first known diagnosis for that individual while one-quarter of diagnoses were of recurrent disease (26%, 460 diagnoses). The number and rate of first known ARF episodes increased from 49 per 100,000 in 2013 (197 diagnoses) to 72 per 100,000 population in 2017 (348 diagnoses), in line with an overall increase in diagnoses. However, the proportion of cases categorised as first known ARF was relatively stable over this period, ranging between 72% and 78% of diagnoses each year.

Figure 3: Number of ARF diagnoses among Indigenous Australians by recurrence status, 2013–2017

Figure 3:  this stacked vertical bar chart shows that the annual increases in the overall number of ARF diagnoses from 2013–2017, is due to increases in both first known diagnoses and recurrent cases. More information is located in the data tables, ARF table 7.

Note: ARF diagnoses include all confirmation statuses by recurrence status. Refer to box 2 and 3 for more information.

Source: AIHW analysis of National Rheumatic Heart Disease data collection.

In each state and territory, the majority of ARF diagnoses were categorised as the first known diagnosis. Over the 5 years to 2017, the average proportion of first known ARF diagnoses in Qld was 71% (between 40 and 130 diagnoses annually). WA reported 76% of ARF diagnoses as first known (248 diagnoses) overall, though the proportion varied from year to year. In SA, an average of 76% of diagnoses were categorised as first known (between 7 and 12 diagnoses annually). There was greater annual variation in SA, because of a smaller number of diagnoses. In NT 70% were first known ARF diagnoses (665 diagnoses), and this was stable over the 5 years.

Figure 4: Proportion of ARF diagnoses among Indigenous Australians by recurrence status 2013-2017

Figure 4: Five vertical stacked bar charts are included, one for each notification year. They show the distribution of first known and recurrent ARF diagnoses, as a proportion of the total, annually for 2013–2017. Around one quarter of ARF episodes are recurrent annually.  More information is located in the data tables, ARF Table 8.

Note: ARF diagnoses include all confirmation statuses by recurrence status. Refer to box 2 and 3 for more information.

Source: AIHW analysis of National Rheumatic Heart Disease data collection.

The proportion of episodes categorised as recurrent increased with age. Over the 5 years, 5% of 0–4 year olds had a recurrent diagnosis compared to 48% of those aged over 45 years. Females were more likely to have recurrent episodes, both overall (28% of diagnoses in females compared with 23% of those in males) and in all age groups except 5–14 year olds.

Recurrent ARF episodes

Around one-quarter of ARF diagnoses reported annually were for recurrent disease. Recurrent episodes were more common in females and in older people.