Recent Infection Testing Algorithm (RITA) as part of routine HIV surveillance in the United
Kingdom
Background
-
An estimated 100,000 people are living with HIV in the UK with approximately 6500 new
diagnoses per year in recent years (Figure 1)
Testing for recent infection among persons newly diagnosed with HIV has been roll out in
England and Northern Ireland as part of routine national public health monitoring since 2009
Test of recent infection are interpreted along side epidemiological and clinical information as
part of a Recent Infection Testing Algorithm (RITA).
The final RITA result is return to the patient and integrated as part of routine HIV surveillance
We report the findings on the first three years of RITA surveillance.
Methods
-
Serum samples from people newly diagnosed with HIV are sent to the Virus Reference
Department at Health Protection Agency Colindale (Flow char)
Samples are tested using a guanine avidity test on the Abbott AxSym HIV 1/2 Og platform.
Include brief Lab methods here and cut-offs (Jenny and Gary)
-
-
Assay results are linked to reports of new diagnoses using pseudo anonymised information
(clinic ID, soundex, dob and gender). Samples taken more than 4 months after the new HIV
diagnosis date are excluded from analyses.
RITA results:
Definition of Recent Infection
o
Avidity score <0.8 and no evidence of severe immunosuppression (a CD4 count < 200
cells/cmm3 and or AIDS within 3 months of diagnosis) or history of antiretroviral therapy
at the time the sample was taken.
Results
ND data: update until December 2011
 Will add coverage map of England and N.I. - yesplease
Total numbers…..coverage over 3 years, % matched
69 cases reclassified as CD4 count <200 cells/mm3 (n=46), report of an AIDs defining illness (n=6) or
on ARV before or at the time the sample was taken (e.g. PEP) (n=17).
-
2009-2011 cumulative RITA results (n=6442), Recent infection rates by exposure group
Probable
exposure
Men who have sex with men
No. of RITA
results
No. Recent
% Recent (95% CI)
2772
617
22.3% (20.723.9%)
category
Men
1115
87
7.8% (6.3-9.5%)
Women
1677
137
8.2% (6.9-9.6%)
Total
2794
224
8.0% (7.0-9.1%)
Injecting drug use
89
6
6.7% (2.5-14.1%)
Other/Not Reported
787
88
11.2% (9.1-13.6%)
6442
935
14.5% (13.7-15.4)
Heterosexual
contact
Total
Recent infection rates by risk group please
Recently acquired HIV infection rates by age n=(6442)
% recent of infection
25
n=165
20
n=382
n=935
15
n=318
n=70
10
5
0
15-24
25-34
Recent infection rates by age among MSM - keep
35-49
50+
ALL
Recently acquired HIV infection rates among MSM by
age (n=2772)
35
n=11
% recent infection
30
n=26
n=61
25
n=203
20
n=3
15
10
5
0
15-24
25-34
35-49
50+
ALL
Recent infection rates by age among heterosexuals- split for men and women
Recently acquired HIV infection rates among
heterosexuals by age (n=2794)
18
n=37
16
% recent infection
14
12
n=83
10
n=224
n=29
8
n=75
6
4
2
0
15-24
Results:
25-34
35-49
50+
ALL
-
Coverage of recent infection testing was (37%) for the 3 years, increasing from 25% in 2009 to
48% in 2011.
Individuals diagnosed with a recent infection have a wide range of avidity scores, with highest
frequencies above 0.70 (n=269; 29%).
Highest rates of recent infection among MSM with over 1 in 5 recently acquired among all
individuals diagnosed
1 in 12 heterosexuals diagnosed with HIV between 2009-2011 had a recent infection
As expected, recent infection rates were also highest among the younger age groups; e.g.
among MSM 1 in 3 aged less than 25 years acquired their infection recently compared to 1 in 8
over 50 years
Conclusions:
-
-
The RITA programme coverage is increasing at a steady rate
Distribution of avidity scores show recency rates are highly sensitive to the cut off value,
particularly if numbers are small; ideally window periods should be studied in the population of
interest
Rates of recent infection indicate high levels of ongoing transmission, particularly among MSM.
Results need to be interpreted in the context of testing patterns to estimate incidence
Further work:
-
Population incidence estimates
Understanding further properties of the avidity test (FRR rates – see abstract no.XXX), CEPHIA
project
Behavioural surveillance among individuals with a recently acquired infection
Role of RITA results in the clinical setting and contact tracing
Acknowledgements:
-
All contributors to the surveillance of HIV and STIs in the UK
References:
1. Janssen RS, Satten GA, Stramer SL, Rawal BD, O'Brien TR, Weiblen BJ et al. New testing strategy to
detect early HIV-1 infection for use in incidence estimates and for clinical and prevention purposes.
JAMA 1998;280:42-8.