A New Method for Estimating the Incidence of Infectious Diseases

Longitudinal assessment of systolic anterior motion of the mitral valve in cats with hypertrophic cardiomyopathy

BACKGROUND

The proportion of cats with hypertrophic cardiomyopathy (HCM) that lose systolic anterior motion of the mitral valve (SAM) in the long term is unknown.

HYPOTHESIS/OBJECTIVES

Cats with HCM will lose SAM in the long term. Loss of SAM will be associated with greater age, longer scan-interval, and altered left ventricular (LV) dimensions.

ANIMALS

Sixty unsedated cats with HCM, not receiving beta blockers or pimobendan.

METHODS

A retrospective cohort study from 2 referral centers. Cats were eligible if they had been diagnosed with HCM and had a repeat echocardiogram ≥1 year later. Clinical and echocardiographic data of the left heart variables were collected.

RESULTS

Thirty-eight cats had SAM at the initial scan. After a median follow-up time of 2.1 years (range: 1.0-5.9), 7 cats had lost SAM (18%) and 5 cats (23%) gained SAM. On follow-up, cats with SAM at the initial scan had a larger left atrium (P = .037), lower left atrial fractional shortening (P = .014), greater LV internal diameter in end-systole (P = .002), and lower LV fractional shortening (P < .001). Four cats with SAM developed congestive heart failure. There were no new cases of congestive heart failure or change in left heart variables in cats without SAM at the initial scan. The gain or loss of SAM was not associated with age or time between scans.

CONCLUSIONS AND CLINICAL IMPORTANCE

Similar proportions of cats gained or lost SAM. Cats with SAM at baseline had more evidence of disease progression than cats without SAM.

HIV treatment-as-prevention and its effect on incidence of HIV among cisgender gay, bisexual, and other men who have sex with men in Australia: a 10-year longitudinal cohort study

BACKGROUND

Although HIV treatment-as-prevention reduces individual-level HIV transmission, population-level effects are unclear. We aimed to investigate whether treatment-as-prevention could achieve population-level reductions in HIV incidence among gay, bisexual, and other men who have sex with men (GBM) in Australia's most populous states, New South Wales and Victoria.

METHODS

TAIPAN was a longitudinal cohort study using routine health record data extracted from 69 health services that provide HIV diagnosis and care to GBM in New South Wales and Victoria, Australia. Data from Jan 1, 2010, to Dec 31, 2019, were linked within and between services and over time. TAIPAN collected data from all cisgender GBM who attended participating services, resided in New South Wales or Victoria, and were 16 years or older. Two cohorts were established: one included HIV-positive patients, and the other included HIV-negative patients. Population prevalence of viral suppression (plasma HIV viral load <200 RNA copies per μL) was calculated by combining direct measures of viral load among the HIV-positive cohort with estimates for undiagnosed GBM. The primary outcome of HIV incidence was measured directly via repeat testing in the HIV-negative cohort. Poisson regression analyses with generalised estimating equations assessed temporal associations between population prevalence of viral suppression and HIV incidence among the subsample of HIV-negative GBM with multiple instances of HIV testing.

FINDINGS

At baseline, the final sample (n=101 772) included 90 304 HIV-negative and 11 468 HIV-positive GBM. 59 234 patients in the HIV-negative cohort had two or more instances of HIV testing and were included in the primary analysis. Over the study period, population prevalence of viral suppression increased from 69·27% (95% CI 66·41-71·96) to 88·31% (86·37-90·35), while HIV incidence decreased from 0·64 per 100 person-years (95% CI 0·55-0·76) to 0·22 per 100 person-years (0·17-0·28). Adjusting for sociodemographic characteristics and HIV pre-exposure prophylaxis (PrEP) use, treatment-as-prevention achieved significant population-level reductions in HIV incidence among GBM: a 1% increase in population prevalence of viral suppression corresponded with a 6% decrease in HIV incidence (incidence rate ratio [IRR] 0·94, 95% CI 0·93-0·96; p<0·0001). PrEP was introduced in 2016 with 17·60% uptake among GBM that year, which increased to 36·38% in 2019. The relationship between population prevalence of viral suppression and HIV incidence was observed before the availability of PrEP (IRR 0·98, 95% CI 0·96-0·99; p<0·0001) and was even stronger after the introduction of PrEP (0·80, 0·70-0·93; p=0·0030).

INTERPRETATION

Our results suggest that further investment in HIV treatment, especially alongside PrEP, can improve public health by reducing HIV incidence among GBM.

FUNDING

National Health and Medical Research Council of Australia.

Hepatitis C incidence among patients attending primary care health services that specialise in the care of people who inject drugs, Victoria, Australia, 2009 to 2020

BACKGROUND

Monitoring trends in hepatitis C virus (HCV) incidence is critical for evaluating strategies aimed at eliminating HCV as a public health threat. We estimate HCV incidence and assess trends in incidence over time among primary care patients.

METHODS

Data were routinely extracted, linked electronic medical records from 12 primary care health services. Patients included were aged ≥16 years, tested HCV antibody negative on their first test recorded and had at least one subsequent HCV antibody or RNA test (January 2009-December 2020). HCV incident infections were defined as a positive HCV antibody or RNA test. A generalised linear model assessed the association between HCV incidence and calendar year.

RESULTS

In total, 6711 patients contributed 17,098 HCV test records, 210 incident HCV infections and 19,566 person-years; incidence was 1.1 per 100 person-years (95% confidence interval (CI): 0.9 to 1.2). Among 559 (8.2%) patients ever prescribed opioid-related pharmacotherapy (ORP) during the observation period, 135 infections occurred during 2,082 person-years (incidence rate of 6.5 per 100 person-years (95% CI: 5.4 to 7.7)). HCV incidence declined 2009-2020 overall (incidence rate ratio per calendar year 0.8 (95% CI: 0.8 to 0.9) and among patients ever prescribed ORT (incidence rate ratio per calendar year 0.9, 95% CI: 0.75 to 1.0).

CONCLUSION

HCV incidence declined among patients at primary care health services including among patients ever prescribed ORP and during the period following increased access to DAA therapy.

SUMMARY

Among a retrospective cohort of ∼6,700 primary care health services patients, this study estimated a hepatitis C virus (HCV) infection incidence of 1.1 per 100 person-years (95% confidence interval: 0.9 to 1.2). HCV infection incidence declined between 2009 and 2020.

Improvements in transition times through the HIV cascade of care among gay and bisexual men with a new HIV diagnosis in New South Wales and Victoria, Australia (2012-19): a longitudinal cohort study

BACKGROUND

Most studies assessing the HIV care cascade have typically been cross-sectional analyses, which do not capture the transition time to subsequent stages. We aimed to assess the longitudinal HIV cascade of care in Australia, and changes over time in transition times and associated factors.

METHODS

In this longitudinal cohort study, we included linked data for gay and bisexual men (GBM) with a new HIV diagnosis who attended clinics participating in the Australian Collaboration for Coordinated Enhanced Sentinel Surveillance in New South Wales and Victoria between Jan 1, 2012, and Dec 31, 2019. We assessed three cascade transition periods: diagnosis to linkage to care (stage 1 transition); linkage to care to antiretroviral therapy (ART) initiation (stage 2 transition); and ART initiation to virological suppression (viral load ≤200 copies per mL; stage 3 transition). We also calculated the probability of remaining virologically suppressed after the first recorded viral load of less than 200 copies per mL. We used the Kaplan-Meier method to estimate transition times and cumulative probability of stage transition.

FINDINGS

We included 2196 GBM newly diagnosed with HIV between 2012 and 2019 contributing 6747 person-years of follow-up in our analysis. Median time from HIV diagnosis to linkage to care (stage 1 transition) was 2 days (IQR 1-3). Median time from linkage to care to ART initiation (stage 2 transition) was 33 days (30-35). Median time from ART initiation to first recorded virological suppression (stage 3 transition) was 49 days (47-52). The cumulative probability of ART initiation within 90 days of linkage to care increased from 36·9% (95% CI 32·9-40·6) in the 2012-13 calendar period to 94·1% (91·2-96·0) in the 2018-19 calendar period and cumulative probability of virological suppression within 90 days of ART initiation increased from 54·3% (48·8-59·3) in the 2012-13 calendar period to 82·9% (78·4-86·4) in the 2018-19 calendar period. 91·6% (90·1-93·1) of GBM remained virologically supressed up to 2 years after their first recorded virological suppression event.

INTERPRETATION

In countries with high cross-sectional cascade estimates such as Australia, the impact of treatment as prevention is better estimated using longitudinal cascade analyses.

FUNDING

National Health and Medical Research Council Australia.