How Many People Are Living with Undiagnosed HIV Infection? An Estimate for Italy, Based on Surveillance Data
OBJECTIVE:
To
estimate the size and characteristics of the undiagnosed HIV population in
Italy in 2012 applying a method that does not require surveillance data from
the beginning of the HIV epidemic.
METHODS:
We
adapted the method known as "London method 2"; the undiagnosed
population is estimated as the ratio between the estimated annual number of
simultaneous HIV/clinical AIDS diagnoses and the expected annual progression
rate to clinical AIDS in the undiagnosed HIV population; the latter is
estimated using the CD4-count distribution of asymptomatic subjects reported to
surveillance. Under-reporting/ascertainment of new diagnoses was also
considered. Also, the total number of PLWHIV was estimated.
RESULTS:
The
undiagnosed HIV population in 2012 was 13,729 (95%CI: 12,152-15,592), 15,102
(13,366-17,151) and 16,475 (14,581-18,710), assuming no
under-reporting/ascertainment, 10% and 20% of under-reporting/ascertainment,
respectively. The percentage of undiagnosed cases was higher among HIV people
aged <25 years (25-28%), MSM (16-19%) and people born abroad (16-19%), while
is small among injection drug users were (3%).
CONCLUSIONS:
The
estimate of people in Italy with undiagnosed HIV in 2012 was in a plausible
range of 12,000-18,000 cases, corresponding to 11-13% of the overall
prevalence. The method is straightforward to implement only requiring annual
information from the HIV surveillance system about CD4-count and clinical stage
at HIV diagnosis. Thus, it could be used to monitor if a certain prevention
initiative lead to the reduction of the undiagnosed HIV population over time.
It can also be easily implemented in other countries collecting the same basic
information from the HIV surveillance system.
- 1"L. Spallanzani" National Institute for Infectious Diseases, IRCCS, Rome, Italy bIstituto Superiore di Sanità , Rome, Italy.
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