Introduction

Late diagnosis of HIV infection remains a critical public health challenge across Europe. According to the latest surveillance data from the European Centre for Disease Prevention and Control (ECDC) and WHO Regional Office for Europe, 48% of all HIV diagnoses in the EU/EEA in 2024 occurred at a late stage (CD4 count <350 cells/µL), while across the broader WHO European Region this proportion reached 54% [1]. Late diagnosis is associated with increased HIV-related morbidity and mortality, poorer response to antiretroviral therapy (ART), increased healthcare costs, and continued HIV transmission [2,3].

In Poland, the epidemiological situation presents particular challenges. In 2022, 2,604 new HIV infections were diagnosed (6.88 per 100,000 population), representing a 78.2% increase compared to the previous year, which coincided with increased population mobility following the conflict in Ukraine [4]. However, it is estimated that approximately 50% of people living with HIV in Poland remain undiagnosed [5]. Recent studies from Polish centres confirm persistently high rates of late presentation, with 53–63% of newly diagnosed patients presenting with CD4 counts below 350 cells/µL [6,7].

To address the challenge of undiagnosed HIV infection, the HIV in Europe initiative proposed indicator condition (IC)-guided testing as an innovative approach to expand HIV testing in healthcare settings [8]. The European HIDES I/II studies (HIV Indicator Diseases Across Europe Study) demonstrated that routine testing of patients presenting with specific indicator conditions, where HIV prevalence exceeds 0.1%, is both effective and cost-effective [9]. This approach has been endorsed by ECDC, WHO, and incorporated into European AIDS Clinical Society (EACS) guidelines [10].

Mononucleosis-like illness (MONO) and community-acquired pneumonia (CAP) represent two important HIV indicator conditions. Primary HIV infection frequently manifests as an acute retroviral syndrome clinically indistinguishable from infectious mononucleosis [11], while recurrent pneumonia is an AIDS-defining condition and HIV-infected individuals have a 5–29 fold higher incidence of pneumonia compared to the general population [12,13].

We previously reported that 58% of patients with mononucleosis-like illness referred to the Hospital for Infectious Diseases in Warsaw missed opportunities for HIV testing due to the absence of a systematic testing programme [14]. Despite endorsement at the European level, prospective data on IC-guided HIV testing remain scarce for Central and Eastern Europe, for Emergency Department settings specifically, and for the complete care cascade following diagnosis. The present study, conducted as part of the European OptTEST project, aimed to evaluate the implementation of IC-guided HIV testing among patients presenting with MONO and CAP in an Emergency Department setting, with the following outcomes: HIV test uptake, HIV seroprevalence, and linkage to HIV care including ART initiation and viral suppression (Fig 1).

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Fig 1. Study flow diagram.

Flow diagram of patient enrolment, HIV testing uptake, and outcomes.

https://doi.org/10.1371/journal.pone.0354485.g001

Materials and methods

Results

HIV prevalence

Twenty-five patients had reactive HIV DUO tests. Of these, 22 (88%) were confirmed positive by Western Blot, yielding an overall HIV prevalence of 3.5% (95% CI: 2.2–5.2%). Prevalence was significantly higher among CAP patients (7/63, 11.1%; 95% CI: 4.6–21.6%) compared to MONO patients (15/573, 2.6%; 95% CI: 1.5–4.3%; p = 0.003). None of the HIV-positive patients had been previously diagnosed. Prevalence estimates use the number of patients tested as the denominator (n = 636) (Table 1).

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Table 1. Characteristics of HIV-positive patients by indicator condition.

https://doi.org/10.1371/journal.pone.0354485.t001

Discussion

This prospective study demonstrates that IC-guided HIV testing in an Emergency Department setting can identify a substantial number of previously undiagnosed HIV infections. The overall HIV prevalence of 3.5% among patients presenting with mononucleosis-like illness and community-acquired pneumonia was 35 times higher than the estimated national HIV prevalence in Poland (0.1%), strongly supporting routine HIV testing in this population [17].

The particularly high HIV prevalence among CAP patients (11.1%) is clinically significant and highlights CAP as a critical indicator condition. All CAP patients who tested HIV-positive presented with advanced disease and severe immunosuppression (median CD4 61 cells/µL), with Pneumocystis jirovecii identified in most cases. These findings are consistent with previous reports demonstrating that respiratory infections in HIV-infected individuals are often the first presentation of AIDS [12,13]. The 100% hospitalization rate among HIV-positive CAP patients underscores the clinical severity of these presentations and the importance of early HIV diagnosis before progression to AIDS-defining illnesses. This prevalence is consistent with, though higher than, the pneumonia-associated prevalence reported in the European HIDES I study [9], and likely reflects both the referral character of our centre and the predominance of Pneumocystis jirovecii pneumonia as an AIDS-defining presentation; the wide confidence interval (95% CI: 4.6–21.6%) warrants cautious interpretation given the small CAP subgroup.

In contrast, patients diagnosed through MONO presented with higher CD4 counts and very high viral loads, suggesting acute or recent HIV infection. This has important public health implications, as individuals with primary HIV infection and high viral loads are disproportionately responsible for HIV transmission [18]. Identifying these patients at the time of their acute retroviral syndrome provides an opportunity for both individual benefit and transmission prevention.

Our findings are particularly relevant in the context of recent epidemiological data from Europe. The 2024 ECDC/WHO surveillance report revealed that 48% of HIV diagnoses in the EU/EEA and 54% across the WHO European Region continue to be made at a late stage [1]. In Poland, recent studies have reported late presentation rates of 53–63% [6,7]. The persistence of high late diagnosis rates despite available effective treatment underscores the urgent need for expanded testing strategies.

The test uptake rate of 71.9% demonstrates good acceptability of routine HIV testing when offered in the context of indicator conditions. This is consistent with findings from other European studies showing that patients generally accept HIV testing when offered by healthcare providers [19,20]. Importantly, the main barrier to testing in our study was not patient refusal but failure to offer the test, particularly during night shifts. This finding highlights the need for systematic implementation of testing protocols that ensure all eligible patients are offered testing regardless of time of presentation.

The excellent linkage to care (100%) and rapid ART initiation (median 8 days) demonstrate that a well-structured testing programme can achieve optimal outcomes across the HIV care cascade. These results align with current recommendations for immediate or rapid ART initiation and suggest that ED-based diagnosis does not impede timely treatment initiation [21].

Several European countries have successfully implemented IC-guided testing strategies. In the United Kingdom, primary care physicians play an important role in HIV detection, and specialty guidelines increasingly recommend HIV testing for patients presenting with indicator conditions [22,23]. Similar programmes have been implemented in Spain, Denmark, and the Netherlands with positive results [24,25]. However, in Poland and many other Central and Eastern European countries, IC-guided testing is not routinely covered by public healthcare, resulting in continued missed opportunities for diagnosis.

This study has several limitations. First, it was conducted at a single specialized infectious diseases hospital, which may receive a higher proportion of patients with severe or atypical presentations compared to general hospitals. However, this also reflects a realistic setting where patients with suspected infectious aetiologies are commonly referred. Second, the study period predates the COVID-19 pandemic, which has had significant impacts on HIV testing and diagnosis across Europe [4]. Third, the relatively small number of CAP patients limits the precision of prevalence estimates in this subgroup. Fourth, eligibility was restricted to patients aged 18–65 years in accordance with the study protocol, which may have led to missed diagnoses among older adults, particularly in the CAP group, in whom pneumonia incidence rises with age.

Despite these limitations, our findings have important policy implications. The substantial yield of new HIV diagnoses (3.5% overall, 11.1% in CAP) far exceeds the 0.1% threshold recommended by European guidelines for routine HIV testing, providing strong justification for implementing IC-guided testing programmes in Polish healthcare settings [8]. The 2022 increase in HIV diagnoses in Poland, partly attributed to migration, further emphasizes the need for accessible testing strategies that can reach diverse populations [4].

From an implementation perspective, IC-guided testing entails modest resource requirements. The cost of a single HIV test is low relative to the lifetime cost of managing late-diagnosed HIV and its complications, and the HIDES studies demonstrated cost-effectiveness wherever HIV prevalence exceeds 0.1%, a threshold far exceeded in our population. In our experience, the protocol added only a few minutes per patient and could be integrated into existing Emergency Department workflows; the principal challenge was organizational, namely ensuring that testing was consistently offered across all shifts, including at night.

Conclusions

This study demonstrates that IC-guided HIV testing among patients presenting with mononucleosis-like illness and community-acquired pneumonia in an Emergency Department setting is feasible, acceptable, and highly effective in identifying previously undiagnosed HIV infections. The HIV prevalence of 3.5% − 35 times higher than the national average – and near-complete linkage to care support the routine implementation of this testing strategy. Given the persistent challenge of late HIV diagnosis in Europe, including Poland, widespread adoption of IC-guided testing could significantly contribute to achieving the UNAIDS 95-95-95 targets and reducing HIV-related morbidity and mortality.

Supporting information

Acknowledgments

We thank the staff of the Emergency Department and HIV Out-Patient Clinic at the Hospital for Infectious Diseases in Warsaw for their contribution to patient recruitment and data collection. We also acknowledge all members of the OptTEST by EuroTEST consortium for their collaboration.