Estimating minimum adult HIV prevalence: a cross-sectional study to assess the characteristics of people living with HIV in Italy

Impact of ART-induced viral suppression on the HIV epidemic in Italy

The present study aims to clarify the role of the fraction of patients under antiretroviral therapy (ART) achieving viral suppression (VS) (i.e. having plasma viral load below the detectability threshold) on the human immunodeficiency virus (HIV) epidemic in Italy. Based on the hypothesis that VS makes the virus untransmittable, we extend a previous model and we develop a time-varying ordinary differential equation model with immigration and treatment, where the naive and non-naive populations of infected are distinguished, and different compartments account for treated subjects virally suppressed and not suppressed. Moreover, naive and non-naive individuals with acquired immune deficiency syndrome (AIDS) are considered separately. Clinical data stored in the nationwide database Antiviral Response Cohort Analysis are used to reconstruct the history of the fraction of virally suppressed patients since highly active ART introduction, as well as to assess some model parameters. Other parameters are set according to the literature and the final model calibration is obtained by fitting epidemic data over the years 2003-2015. Predictions on the evolution of the HIV epidemic up to the end of 2035 are made assuming different future trends of the fraction of virally suppressed patients and different eligibility criteria for treatment. Increasing the VS fraction is found to reduce the incidence, the new cases of AIDS and the deaths from AIDS per year, especially in combination with early ART initiation. The asymptotic properties of a time-invariant formulation of the model are studied, and the existence and global asymptotic stability of a unique positive equilibrium are proved.

Low bone mineral density in HIV-positive young Italians and migrants

BACKGROUND

Human immunodeficiency virus (HIV) infected individuals may have osteoporosis. We aimed to evaluate the bone mineral density (BMD) in naïve antiretroviral (ARV) treated HIV positive patients comparing native Italian group (ItG) to a Migrants group (MiG) upon arrival in Italy.

METHODS

We conducted a cross-sectional study on 83 HIV patients less than 50 years old. We used the dual-energy X-ray absorptiometry (DXA) within six months from the HIV diagnosis. Participants were categorized as having low BMD if the femoral neck or total lumbar spine Z-score was- 2 or less.

RESULTS

MiG showed low BMD more often than ItG (37.5% vs.13.6%), especially for the female gender (16.7% vs. 0.0%). A low CD4 rate (<200 cells/μl) was most often detected in MiG than ItG. In particular, we found most often male Italians with abnormal CD4 than male migrants (67.8% vs. 33.3%) and vice versa for females (30.5% vs. 66.7%). We found an abnormal bone mineral density at the lumbar site. Low BMD at the lumbar site was more frequently observed in female migrants than female Italians. Both male and female migrants had a Z-score value significantly lower than male and female Italians, respectively. By logistic regression low vitamin-D level was positively correlated to low BMD in ItG only. All data were verified and validated using a triple code identifier.

CONCLUSIONS

Both DXA and vitamin-D evaluation should be offered after the diagnosis of HIV infection. Lumbar site low BMD is an initial condition of bone loss in HIV young patients, especially in female migrants. Vitamin D levels and supplementation may be considered after HIV diagnosis independently of age to improve bone health.

HIGHLIGHTS

This study evaluates the frequency of bone mineral density in HIV positive patients naive to antiretroviral therapy. It compares the density of the native Italian population with that of HIV Migrants upon arrival in Italy. The results show that HIV positive migrants, even if younger than 50 years of age, are at risk for osteoporosis, especially if they are female.

Is it Safe and Cost Saving to Defer the CD4+ Cell Count Monitoring in Stable Patients on Art with More than 350 or 500 cells/μl?

Background

CD4+ lymphocyte cell count represents the main immunological marker used to monitor HIV infection. However, frequent monitoring may be unnecessary, could cause anxiety to the patient as well as burdening healthcare with extra expenses.

Objectives and methods

A two-step retrospective (safety and cost-saving) analysis was performed to evaluate the probability of maintaining a safe number of more than 350 CD4+ cells/μl in HIV-positive subjects under treatment during a three-year follow up and secondarily to estimate in real life the cost of the CD4+ determinations in a 3 years period, speculating on possible cost-saving strategies. The safety analyses was conducted with Kaplan-Meyer method considering: 1) all patients independently from their viral load (VL); 2) patients with 500 > CD4+ ≥ 350 cells/μl versus (vs) CD4+ ≥ 500 cells/μl at baseline; 3) patients with VL < 20 copies/ml vs VL > 20 copies/ml. The cost-saving analysis measuring the costs of CD4+ determinations was calculated from April 1, 2013, to March 31, 2016.

Results

In the safety analysis, 253 subjects were enrolled. The median CD4+ count was 623 (489–805) cells/μl. Subjects maintaining ≥ 350 cells/μl in the first, second, and third year were respectively 238 (94.1%), 229 (90.5%), and 226 (89.3%), independently from VL. Within subjects with ≥ 350 CD4+/μl vs. ≥ 500 CD4+/μl at baseline, those who maintained ≥ 350 cells/μl until the third year were respectively 241 (95.3%) and 158 (98.1%). The probability of maintaining these values in the third year was 89.3% for those who had CD4+ ≥ 350/μl at baseline and 98.1% for those who had CD4+ ≥ 500/μl. This probability was around 90% vs. 99% for subjects with HIV-RNA above or below 20 copies/ml. In the real-life cost saving analysis, we evaluated subjects with a stable value or more than 500 CD4+ (respectively 343, 364 and 383 in the first, second and third period). We observed mean value of about two determinations patient/year (2.41 in 2013/2014; 2.32 in 2014/2015; 2.18 in 2015/2016), with a significant decrease between the first and the last period (p<0.001). The mean cost patient/year was €101.51 in the first year, €97.61 in the second, €92.00 in the third (p<0,001). Assuming to extend these procedures to all our patients with stable CD4+ cells/μl and monitoring CD4+ cell count once in a year, we were able to obtain an overall saving of €19,152/year.

Conclusions

A very high percentage of subjects maintained a high and safe number of CD4+ cells (>350 cells/μl) during a three-year follow-up. It could be possible to save up to 66% of the costs by reducing the number of CD4+ count determinations in a year, to have other favorable consequences as well, releasing new resources for patient management.

People living with undiagnosed HIV infection and a low CD4 count: estimates from surveillance data, Italy, 2012 to 2014

Background and aims

Late HIV diagnosis is associated with onward HIV transmission, higher morbidity, mortality and healthcare costs. In Italy, more than half of people living with HIV were diagnosed late during the last decade, with a CD4 count < 350 cells/mm³ at diagnosis. We aimed to determine the number and characteristics of people living with undiagnosed HIV infection and low CD4 counts in Italy.

Methods

Data on newly reported HIV diagnoses from 2012 –2014 were obtained from the national HIV surveillance system. We used the European Centre for Disease Prevention and Control HIV modelling tool to calculate the undiagnosed prevalence and yearly diagnosed fraction (YDF) in people with low CD4 count.

Results

The estimated annual number undiagnosed HIV infections with low CD4 count was on average 6,028 (95% confidence interval (CI): 4,954–8,043) from 2012–2014. In 2014, most of the undiagnosed people with low CD4 count were men (82.8%), a third acquired HIV through sex between men (MSM) (35.0%), and heterosexual transmission (33.4%), respectively. The prevalence of undiagnosed HIV infection was 11.3 (95% CI: 9.3–14.9) per 100,000 residents ranging from 0.7 to 20.8 between Italian regions. Nationally the prevalence rate was 280.4 (95% CI: 173.3–450.2) per 100,000 MSM, 8.3 (95% CI: 4.9–13.6) per 100,000 heterosexual men, and 3.0 (95% CI: 1.4–5.6) per 100,000 women. The YDF was highest among heterosexual women (27.1%; 95% CI: 16.9–45.2%).

Conclusions

These findings highlight the importance of improving efforts to identify undiagnosed HIV infections primarily among men, both MSM and heterosexual men.

Towards achieving the fast-track targets and ending the epidemic of HIV/AIDS in Ethiopia: Successes and challenges

BACKGROUND

Ethiopia has adopted the global plan to end the epidemic of HIV/AIDS. The aim of this study was to assess the progress made towards achieving this plan.

METHODS

A review and analysis of national population-based surveys, surveillance, and routine programme data was executed. The data analysis was conducted using Excel 2016 and Stata 14 (StataCorp LP, College Station, TX, USA).

RESULTS

Between 2011 and 2016, the number of HIV-related deaths dropped by 58%, while that of new HIV infections dropped by only 6%. Discriminatory attitudes declined significantly from 77.9% (95% confidence interval (CI) 77.3-78.4%) in 2011 to 41.5% (95% CI 40.6-42.4%) in 2016. Around 79% of adult people living with HIV (PLHIV) were aware of their HIV status; 90% of PLHIV who were aware of their HIV status were taking antiretroviral treatment (ART) and 88% of adult PLHIV on ART had viral suppression in 2016. The proportion of people aged 15-49 years who had ever been tested for HIV and had received results increased from 39.8% (95% CI 39.2-40.4%) in 2011 to 44.8% (95% CI 44.2-45.4%) in 2016. This proportion was very low among children below age 15 years at only 6.2% (95% CI 5.9-6.5%). Among regions, HIV testing coverage varied from 13% to 72%. Female sex workers had lower coverage for HIV testing (31%) and ART (70%) than the national average in the adult population. International funding for HIV dropped from more than US$ 1.3 billion in 2010-2012 to less than US$ 800 million in 2016-2018.

CONCLUSIONS

Ethiopia is on track to achieve the targets for HIV testing, ART, viral suppression, and AIDS-related deaths, but not for reductions in new HIV infections, discriminatory attitudes, and equity. Ending the epidemic of HIV/AIDS requires a combined response, including prevention and treatment, tailored to key populations and locations, as well as increased funding.

Impact of comorbidity on the risk and cost of hospitalization in HIV-infected patients: real-world data from Abruzzo Region

Background

Due to the success of antiretroviral therapy, human immunodeficiency virus (HIV) infection has been transformed into a lifelong condition. In Italy, little is known about the impact of comorbidities (CMs) on the risk of hospitalization and related costs for people who live with HIV (PWLHIV). The objective of the study was to quantify the risk of hospitalization and costs associated with CMs in an Italian cohort of PWLHIV.

Methods

The study population included subjects aged ≥18 years with HIV infection, identified in the Abruzzo’s hospital discharge database among files stored from 2004 until 2013 and then followed up until December 2015. Patients’ CMs (Charlson Comorbidity Index [CCI)] were extracted from International Classification of Diseases, Ninth Revision, Clinical Modification codes in the hospital discharge abstracts. Poisson regression was used to compare the incidence rate of hospital admissions in patients with and without each CM class. Incidence rate ratios (IRRs) with 95% confidence intervals (CIs) were adjusted for age, sex and the other CMs. A generalized linear model under gamma distribution was used to estimate adjusted mean hospital costs. Costs were derived from official Italian Diagnosis-related group (DRG) based reimbursements.

Results

Among 1,026 HIV patients identified (mean age 47 years), 30% had at least one CM and 14.5% underwent hospital admission during the follow-up period. The risk of acute hospitalization significantly increased among patients with hepatitis C virus (HCV) coinfection (adjusted IRR 1.98; 95% CI: 1.59–2.47), renal (adjusted IRR 2.27; 95% CI: 1.45–3.56), liver (adjusted IRR 2.21; 1.57–3.13) and chronic pulmonary CMs (adjusted IRR 2.31; 1.63–3.32). Adjusted mean hospital costs were €2,494 in patients without CMs and €4,422 and €9,734 in those with CCI=1 or CCI ≥2, respectively.

Conclusion

The presence of renal, liver and chronic pulmonary CMs, as well as HCV coinfection doubled the risk of hospitalization in the PWLHIV cohort. A CCI ≥2 is associated with a fourfold increase in hospitalization costs. Our study provides new evidence that CMs in PWLHIV increase the risk of hospitalization and local health service facilities.

A simple model of HIV epidemic in Italy: The role of the antiretroviral treatment

In the present paper we propose a simple time-varying ODE model to describe the evolution of HIV epidemic in Italy. The model considers a single population of susceptibles, without distinction of high-risk groups within the general population, and accounts for the presence of immigration and emigration, modelling their effects on both the general demography and the dynamics of the infected subpopulations. To represent the intra-host disease progression, the untreated infected population is distributed over four compartments in cascade according to the CD4 counts. A further compartment is added to represent infected people under antiretroviral therapy. The per capita exit rate from treatment, due to voluntary interruption or failure of therapy, is assumed variable with time. The values of the model parameters not reported in the literature are assessed by fitting available epidemiological data over the decade 2003÷2012. Predictions until year 2025 are computed, enlightening the impact on the public health of the early initiation of the antiretroviral therapy. The benefits of this change in the treatment eligibility consist in reducing the HIV incidence rate, the rate of new AIDS cases, and the rate of death from AIDS. Analytical results about properties of the model in its time-invariant form are provided, in particular the global stability of the equilibrium points is established either in the absence and in the presence of infected among immigrants.

Continuum of care among HIV-1 positive patients in a single center in Italy (2007-2017)

AIM

This study aimed to determine rates of retention in care, viral suppression, and use of antiretroviral therapy (ART) and identify risk factors for loss to follow-up (FU) in an adult cohort from a tertiary teaching hospital in Florence, Italy.

METHODS

We included all newly diagnosed HIV-infected patients aged >18 years who were linked to our clinic from July 2007 to December 2015. On July 31, 2017, we evaluated the proportion of patients retained in care, on ART, and having HIV RNA <50 copies/mL. We assessed predictors of loss to FU through univariate and multivariate analyses.

RESULTS

We included 423 patients. By July 2017, 23 (5.5%) patients died, 25 (5.9%) moved to a different center, and 64 (15.1%) were lost to follow-up. Among the remaining 311 patients (73.5%), 96.5% were on ART and 95% had HIV RNA <50 copies/mL. After adjustment for sex, age at diagnosis, origin, and risk of transmission, our results showed a lower retention rate in those not on ART at the end of the follow-up (adjusted HR [aHR]: 10.33, 95% CI 5.80-18.40, P<0.001), non-Italians (aHR: 1.69, 95% CI: 0.99-2.89, P=0.054) and <35 years old (aHR: 1.85; 95% CI 1.04-3.30, P=0.037).

CONCLUSION

In our hospital in Florence, we found a gap in retention in care among foreigners, people <35 years old, and those who were not in treatment at the end of the follow-up. The results of this study may help to identify opportunities for appropriate future interventions.

People diagnosed with HIV and in care in Italy in 2014: results from the second national survey

We conducted a second National survey in all Italian Infectious Disease clinics to assess the number of people diagnosed and linked to care and, among these, the number of people on antiretroviral therapy and viral load suppressed. In 2014, 100,049 (0.16 per 100 residents) people diagnosed and linked to care were estimated, corresponding to an increase of 6.3% compared to the survey conducted in 2012. Among people diagnosed and linked to care, 91.9% were on antiretroviral therapy (increase of 11.4% compared to 2012), and among these, 87.7% were viral load suppressed. Overall, the majority were males (72.1%), Italians (82.7%), aged 25-49 years (45.6%); the most common HIV mode of transmission was reported to be in heterosexual contact (37.9%) and men who had sex with men (31.3%); 8.8% had less than 350 CD4 cells/μL, 82.4% had VL <50 copies and 22.9% had a CDC stage C. In conclusion, the number of people diagnosed and linked to care was increasing. The vast majority of them was receiving ART but the percentage of people still with a detectable viral load was lower than the 90-90-90 WHO target.

The Human Immunodeficiency Virus Continuum of Care in European Union Countries in 2013: Data and Challenges

BACKGROUND.

The Joint United Nations Programme on HIV/AIDS (UNAIDS) has set a "90-90-90" target to curb the human immunodeficiency virus (HIV) epidemic by 2020, but methods used to assess whether countries have reached this target are not standardized, hindering comparisons.

METHODS.

Through a collaboration formed by the European Centre for Disease Prevention and Control (ECDC) with European HIV cohorts and surveillance agencies, we constructed a standardized, 4-stage continuum of HIV care for 11 European Union countries for 2013. Stages were defined as (1) number of people living with HIV in the country by end of 2013; (2) proportion of stage 1 ever diagnosed; (3) proportion of stage 2 that ever initiated ART; and (4) proportion of stage 3 who became virally suppressed (≤200 copies/mL). Case surveillance data were used primarily to derive stages 1 (using back-calculation models) and 2, and cohort data for stages 3 and 4.

RESULTS.

In 2013, 674500 people in the 11 countries were estimated to be living with HIV, ranging from 5500 to 153400 in each country. Overall HIV prevalence was 0.22% (range, 0.09%-0.36%). Overall proportions of each previous stage were 84% diagnosed, 84% on ART, and 85% virally suppressed (60% of people living with HIV). Two countries achieved ≥90% for all stages, and more than half had reached ≥90% for at least 1 stage.

CONCLUSIONS.

European Union countries are nearing the 90-90-90 target. Reducing the proportion undiagnosed remains the greatest barrier to achieving this target, suggesting that further efforts are needed to improve HIV testing rates. Standardizing methods to derive comparable continuums of care remains a challenge.

HIV-Positive Individuals on Antiretroviral Therapy and with Viral Load Suppressed in 12 Infectious Diseases Clinics in Italy: Successes and Disparities in the HIV Continuum of Care

The HIV care continuum is a tool that describes the quality of HIV care for people living with HIV and assesses the extent to which the goal of viral suppression has been achieved. In 2014, we conducted a retrospective cross-sectional study to assess the characteristics associated with three steps of the HIV continuum of care in Italy [i.e., most recent diagnoses, people diagnosed and in care who are on therapy, and people with viral load (VL) suppressed among those on therapy]. Among the 10,262 individuals diagnosed and linked to care, 9,810 (95.6%) were on therapy and among these 8,383 (85.7%) had VL suppressed. The comparison between people diagnosed in 2013 to those diagnosed before 2013 shows that they were more likely to be male [adjusted odds ratios (AOR) = 1.46; 95% confidence interval (95% CI): 1.18-1.79], <25 years of age (AOR = 7.59; 95% CI: 4.17-13.79), and born in Italy (AOR = 1.33; 95% CI: 1.09-1.62). Factors significantly associated with not being in therapy were as follows: age <35 years (AOR = 4.03; 95% CI: 2.50-6.51), age 35-55 years (AOR = 1.85; 95% CI: 1.19-2.87), being migrants (AOR = 1.25; 95% CI: 1.13-1.39), being men who have sex with men (MSM) (AOR = 1.54; 95% CI: 1.22-1.95), have been diagnosed in 2010-2012 (AOR = 4.51; 95% CI: 3.03-6.73), or before 2010 (AOR = 3.18; 95% CI: 2.41-4.21), and not had previous clinical AIDS (AOR = 8.24; 95% CI: 3.33-20.23), whereas factors significantly associated with not having VL suppressed were as follows: age <35 years (AOR = 1.56; 95% CI: 1.13-2.13) and age 35-55 years (AOR = 1.23; 95% CI: 1.10-1.38), being migrants (AOR = 1.38; 95% CI: 1.11-1.70), have been diagnosed in 2010-2012 (AOR = 1.34; 95% CI: 1.14-1.57), in 2013 (AOR = 4.35; 95% CI: 2.47-7.68), and not having had previous clinical AIDS (AOR = 0.74; 95% CI: 0.63-0.86). Despite this we observed significant disparities for young people, MSM, and migrants, overall in Italy the vast majority of people diagnosed with HIV and in care in 2013 received therapy and the percentage of people who are VL suppressed is near the Joint United Nations Programme on HIV/AIDS goal.

Multiple cause-of-death data among people with AIDS in Italy: a nationwide cross-sectional study

Background

Multiple cause-of-death (MCOD) data allow analyzing the contribution to mortality of conditions reported on the death certificate that are not selected as the underlying cause of death. Using MCOD data, this study aimed to fully describe the cause-specific mortality of people with AIDS (PWA) compared to people without AIDS.

Methods

We conducted a nationwide investigation based on death certificates of 2,515 Italian PWA and 123,224 people without AIDS who had died between 2006 and 2010. The conditions most frequently associated with PWA mortality, compared to people without AIDS, were identified using an age-standardized proportion ratio (ASPR) calculated as the ratio between the age-standardized proportion of a specific cause among PWA and the same proportion among people without AIDS.

Results

The most frequently reported conditions at death among PWA were infectious/parasitic diseases (52%), digestive (36%), respiratory (33%), and circulatory (32%) system diseases, and neoplasms (29%). All AIDS-defining conditions resulted highly associated (ASPR significantly greater than unity) with PWA deaths. Significant associations also emerged for leishmaniasis (ASPR = 188.0), encephalitis/myelitis/encephalomyelitis (ASPR = 14.3), dementia (ASPR = 13.1), chronic viral hepatitis (ASPR = 13.1), liver fibrosis/cirrhosis (ASPR = 4.4), pneumonia (ASPR = 4.4), anal (ASPR = 12.1) and liver (ASPR = 1.9) cancers, and Hodgkin’s disease (ASPR = 3.1).

Conclusions

Study findings identified the contribution of several non-AIDS-defining conditions on PWA mortality, emphasizing the need of preventive public health interventions targeting this population.

Can the UNAIDS 90-90-90 target be achieved? A systematic analysis of national HIV treatment cascades

Background

In 2014, the Joint United Nations Programme on HIV and AIDS (UNAIDS) and partners set the ‘90-90-90 targets’; aiming to diagnose 90% of all HIV positive people, provide antiretroviral therapy (ART) for 90% of those diagnosed and achieve viral suppression for 90% of those treated, by 2020. This results in 81% of all HIV positive people on treatment and 73% of all HIV positive people achieving viral suppression. We aimed to analyse how effective national HIV treatment programmes are at meeting these targets, using HIV care continuums or cascades.

Methods

We searched for HIV treatment cascades for 196 countries in published papers, conference presentations, UNAIDS databases and national reports. Cascades were constructed using reliable, generalisable, recent data from national, cross-sectional and longitudinal study cohorts. Data were collected for four stages; total HIV positive people, diagnosed, on treatment and virally suppressed. The cascades were categorised as complete (four stages) or partial (3 stages), and analysed for ‘break points’ defined as a drop >10% in coverage between consecutive 90-90-90 targets.

Results

69 country cascades were analysed (32 complete, 37 partial). Diagnosis (target one—90%) ranged from 87% (the Netherlands) to 11% (Yemen). Treatment coverage (target two—81% on ART) ranged from 71% (Switzerland) to 3% (Afghanistan). Viral suppression (target three—73% virally suppressed) was between 68% (Switzerland) and 7% (China).

Conclusions

No country analysed met the 90-90-90 targets. Diagnosis was the greatest break point globally, but the most frequent key break point for individual countries was providing ART to those diagnosed. Large disparities were identified between countries. Without commitment to standardised reporting methodologies, international comparisons are complex.

Trigger-oriented HIV testing at Internal Medicine hospital Departments in Northern Italy: an observational study (Fo.C.S. Study)

BACKGROUND

Early detection of undiagnosed HIV infected patients is of paramount importance. The attitude of Italian hospital-based Internal Medicine physicians to prescribe HIV testing following the detection of HIV-associated signs, symptoms and behaviours (triggers) has been reported to be poor. The aim of the study is to quantify the extent of the missed opportunities for early HIV diagnosis in Internal Medicine Departments (IMD).

METHODS

Patients admitted to IMD of a General University Hospital in Italy in March-June 2013 were interviewed using a structured questionnaire investigating the presence of triggers for HIV testing, including patient's characteristics, symptoms and conditions associated with HIV infection. HIV tests performed during hospitalisation were recorded.

RESULTS

HIV testing was performed in 73 (6.6%) out of 1113 hospitalisations (1072 patients), providing positive results in three cases (4.1%). All of them presented ≥1 triggers. Conversely, 853 triggers were identified in 528 hospitalisations with at least one trigger (47.4%). The proportion of hospitalisations where an HIV testing was prescribed was 3.1%, 9.5% and 16.0% in the presence of zero, one-to-two or more triggers, respectively. Age <70 years, female gender, length of hospital stay, haematological disease, HBV infection, multiple sexual partners and lymphadenopathy were predictors of HIV testing by logistic regression analysis.

CONCLUSIONS

Although chances of an HIV test being performed in patients hospitalised in IMD increases along with the number of triggers, the number of tests being performed in people presenting with triggers is unacceptably low and requires educational interventions in order to obtain individual and public health advantages.

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⁺ cell count distribution of asymptomatic patients reported to surveillance. Under-reporting/ascertainment of new diagnoses was also considered. Also, the total number of people living with HIV was estimated.

Results:

The undiagnosed HIV population in 2012 was 13 729 (95% confidence interval: 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 below 25 years (25–28%), MSM (16–19%) and people born abroad (16–19%), whereas it was small among injection drug users (3%).

Conclusion:

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⁺ cell 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.