Declining prevalence of AIDS-defining illness among newly diagnosed people living with HIV in northern Thailand: a 10-year review

Abstract

Background

HIV infection and AIDS remain serious global health problems. In Thailand, previous studies have revealed that nearly half of newly diagnosed people living with HIV (PLWH) presented with AIDS-defining illnesses (ADIs). However, data regarding the burden of ADIs among PLWH in northern Thailand have been limited.

Methods

This retrospective cohort study analyzed 777 newly diagnosed PLWH between January 1, 2012, and December 31, 2022 at a tertiary care hospital in northern Thailand.

Results

The study found that 29.0% of patients presented with ADIs at diagnosis, although this prevalence showed a significant decreasing trend over time (p-value = 0.021). Among the 552 patients without ADIs, 57.2% were asymptomatic at diagnosis. The most common ADIs were pneumocystis pneumonia (42.7%), talaromycosis (27.1%), and pulmonary tuberculosis (14.2%). Median CD4 counts at diagnosis were markedly lower in patients with ADIs [34 (IQR 16–83) cells/cu.mm] compared with those without ADIs [293 (IQR 183–437) cells/cu.mm]. Overall, 25.5% of newly diagnosed PLWH required hospitalization, with rates of 72.0% in those with ADIs and 6.5% in those without.

Conclusions

Despite widespread availability of combination antiretroviral therapy (cART), a substantial proportion of PLWH in northern Thailand continue to be diagnosed at an advanced stage, underscoring the urgent need to strengthen HIV screening and early diagnosis strategies.

Background

Human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) continue to pose a major challenge to global health. In 2023, approximately 39.9 million people worldwide were living with HIV (PLWH) [1]. In that year, 1.3 million people were newly diagnosed with HIV and 630,000 deaths were attributed to AIDS-defining illnesses (ADIs) [1]. Since 2010, the global incidence of new HIV infections has decreased by 39%, from 2.1 million to 1.3 million in 2023 [1]. In Thailand, an estimated 580,000 adults aged 15 years and older were living with HIV in 2023, with 9,000 new cases reported that year [2]. In addition, 12,000 HIV-infected patients in Thailand died from ADIs in 2023. Over the past decade, the number of newly diagnosed people living with HIV (PLWH) and AIDS-related deaths in Thailand has steadily declined [2].

Despite the widespread use of combination antiretroviral therapy (cART) since 1996 [3], the prevalence of late HIV presentations and opportunistic infections (OIs) has not declined significantly in Asia [4–6], in contrast to other countries [7, 8]. Two studies in Thailand reported that 30–50% of newly diagnosed HIV infections presented with ADIs [4, 6].

The clinical presentation and OIs vary by geographical area [9, 10]. In Thailand, common ADIs include tuberculosis (both pulmonary and extrapulmonary), cryptococcosis, Pneumocystis jirovecii pneumonia (PJP) and cytomegalovirus (CMV) infections [4, 6, 10, 11]. In particular, disseminated Mycobacterium avium complex (MAC) infection and talaromycosis are more common in northern Thailand [9]. However, data on the clinical presentation of newly diagnosed PLWH in northern Thailand remain limited. The aim of this study is to determine the prevalence of ADIs among newly diagnosed PLWH and to evaluate the clinical presentation, hospitalization rate and in-hospital mortality.

Methods

We conducted a retrospective cohort study from January 1, 2012, to December 31, 2022, at Maharaj Nakorn Chiang Mai Hospital, a 1,400-bed tertiary care hospital in northern Thailand. Eligible participants were individuals aged 18 years and older with confirmed HIV diagnosis based on reactive results from three serologic tests performed at the hospital. Both inpatient and outpatient cases were included.

Cases were initially identified using International Classification of diseases (ICD)-10 codes B20–B24. All cases were subsequently reviewed by clinical reviewers to confirm the diagnoses based on supporting clinical, microbiological, radiological, and/or histopathological evidence, as appropriate. Data collected included baseline characteristics (age, sex, underlying diseases, and route of HIV transmission), clinical presentations (symptoms and presence or absence of ADIs, with ADI diagnoses according to the revised 2014 Centers for Disease Control and Prevention (CDC) classification) [12] and laboratory findings (complete blood count; renal and liver function tests; CD4 count and HIV viral load at the time of diagnosis, at six and twelve months after treatment).

Co-infections with HBV or HCV or syphilis, as well as microbiological and radiological findings, were also assessed. For hospitalized patients, admission date, discharge date, length of stay, and mortality rate were recorded.

Categorical data are presented as frequencies and percentages, while continuous data are presented as the mean and standard deviation (SD) or the median and interquartile range (IQR), depending on data distribution. Comparisons between groups were performed using the Chi-square test or Fisher’s exact test for categorical variables and the Student’s t-test for continuous variables. Trends were analyzed using the Cochran-Armitage test. Factors associated with ADIs identified in univariate analysis with a p-value < 0.10 were included in the multivariable analysis using a backward stepwise procedure. A p-value < 0.05 was considered statistically significant. All statistical analyzes were performed using Stata statistical software, version 17 (Stata Statistical Software: Release 17.0, Stata Corporation, College Station, TX, 2021).

Results

During the study period, 777 people were newly diagnosed with HIV, including 225 (29.0%) with ADIs and 552 (71.0%) without ADIs (Fig. 1). The prevalence of ADIs among newly diagnosed PLWH showed a decreasing trend over time (p = 0.021) (Fig. 2). Of the 777 individuals, 317 were asymptomatic, with 316 having no ADIs. The common reasons for HIV testing were unprotected sex (N = 137, 43.2%), having an HIV-positive partner (N = 54, 17.0%), preoperative evaluation (N = 35, 11.0%) and notification after blood donation (N = 25, 7.9%). Only one patient with an ADI was identified during a routine health screening and was diagnosed with invasive cervical cancer.

Fig. 1.

Numbers of people living with HIV (PLWH) with and without AIDS-defining illnesses (ADIs) by year

Fig. 2.

Percentages of newly diagnosed people living with HIV (PLWH) with AIDS-defining illnesses by year

Among patients with ADIs, the median (IQR) age at diagnosis was 37 (28, 46) years. Males comprised 72.9% (164 patients) of this group. The primary routes of HIV transmission were heterosexual (54.7%), homosexual (39.6%) and needle sharing (injection drug use or tattooing) (16.4%). In contrast, among patients without ADIs, the median (IQR) age at diagnosis was 27 [22, 36] years and 83.0% were male (458 patients). The main transmission routes of this group were homosexual (65.5%), heterosexual (31.2%) and needle sharing (9.6%). Almost 80% of newly diagnosed PLWH had no underlying diseases (Table 1).

Table 1.

Baseline characteristics of newly diagnosed people living with HIV with and without AIDS-defining illnesses

Characteristics	With ADIs (N = 225)	Without ADIs (N = 552)	P-value
Male	164 (72.9)	458 (83.0)	0.002
Age at diagnosis	37 (28, 46)	27 (22, 36)	< 0.001
Underlying diseases	49 (21.8)	126 (22.8)	0.777
• Diabetes	9 (4.0)	10 (1.8)	0.120
• Hypertension	9 (4.0)	28 (5.1)	0.583
• Dyslipidemia	6 (2.7)	16 (2.9)	1.000
• Chronic kidney disease	1 (0.4)	2 (0.4)	1.000
• Hematologic diseases	9 (4.0)	21 (3.8)	0.841
• Others	28 (12.4)	78 (14.1)	0.567
Route of transmission
• Heterosexual	123 (54.7)	172 (31.2)	< 0.001
• Homosexual	89 (39.6)	356 (65.5)	< 0.001
• Bisexual	4 (1.8)	17 (3.1)	0.310
• Sharing needles (IVDU, tattooing)	37 (16.4)	53 (9.6)	0.007
• Maternal to child	0 (0)	1 (0.2)	1.000

Data are presented as number (%)

Abbreviations: ADIs, acquired immunodeficiency syndrome (AIDS)-defining illnesses; HBV, hepatitis B virus; HCV, hepatitis C virus; HIV, human immunodeficiency virus; IVDU, intravenous drug use; PLWH, people living with HIV

The most common symptoms in PLWH with ADIs were fever (74.2%), weight loss (71.6%), cough (62.7%) and mucocutaneous lesions (57.3%, mainly pruritic papular eruptions). In contrast, 57.2% of PLWH without ADIs were asymptomatic, with the most common symptoms being mucocutaneous lesions (24.1%, mainly maculopapular rash), weight loss (14.9%), fever (12.7%) and lymphadenopathy (11.2%). In PLWH without ADIs, sore throat, maculopapular rash, condyloma acuminata, herpes zoster and genital ulcers were more common than those with ADIs (Table 2).

Table 2.

Clinical manifestations in newly diagnosed people living with HIV with and without AIDS-defining illnesses

Clinical manifestations	PLWH with ADIs (N = 225)	PLWH without ADIs (N = 552)	P-value
Constitutional signs and symptoms	210 (93.3)	131 (23.7)	< 0.001
• Fever	167 (74.2)	70 (12.7)	< 0.001
• Fatigue	89 (39.6)	30 (5.4)	< 0.001
• Weight loss	161 (71.6)	82 (14.9)	< 0.001
• Loss of appetite	100 (44.4)	36 (6.5)	< 0.001
• Myalgia	16 (7.1)	19 (3.4)	0.035
• Night sweat	33 (14.7)	2 (0.4)	< 0.001
Neurological signs and symptoms	35 (15.6)	23 (4.2)	< 0.001
• Headache	21 (9.3)	16 (2.9)	< 0.001
• Seizure	5 (2.2)	2 (0.4)	0.024
• Alteration of consciousness	8 (3.6)	0 (0)	< 0.001
• Visual disturbance	8 (3.6)	3 (0.5)	0.003
• Weakness	6 (2.7)	1 (0.2)	0.003
• Numbness	2 (0.9)	3 (0.5)	0.630
Respiratory signs and symptoms	152 (67.6)	51 (9.2)	< 0.001
• Sore throat	9 (4.0)	25 (4.5)	0.848
• Cough	141 (62.7)	32 (5.8)	< 0.001
• Hemoptysis	4 (1.8)	0 (0)	0.007
• Dyspnea	108 (48.0)	12 (2.2)	< 0.001
• Desaturation	70 (31.1)	1 (0.2)	< 0.001
Gastrointestinal signs and symptoms	73 (32.4)	40 (7.3)	< 0.001
• Odynophagia	6 (2.7)	1 (0.2)	0.003
• Vomiting	19 (8.4)	10 (1.8)	< 0.001
• Diarrhea	28 (12.4)	21 (3.8)	< 0.001
• Jaundice	3 (1.3)	5 (0.9)	0.697
• Abdominal pain	18 (8.0)	10 (1.8)	< 0.001
• Hepatomegaly	18 (8.0)	4 (0.7)	< 0.001
• Splenomegaly	19 (8.4)	4 (0.7)	< 0.001
Mucocutaneous lesions	129 (57.3)	133 (24.1)	< 0.001
• Oral thrush	90 (40.0)	28 (5.1)	< 0.001
• Oral ulcer	9 (4.0)	3 (0.5)	0.001
• Umbilicated lesions	27 (12.0)	0 (0)	< 0.001
• Pruritic papular eruption	40 (17.8)	27 (4.9)	< 0.001
• Maculopapular rash	3 (1.3)	34 (6.2)	0.003
• Condyloma acuminata	2 (0.9)	22 (4.0)	0.022
• Herpes zoster	1 (0.4)	14 (2.5)	0.080
• Genital ulcer	3 (1.3)	11 (2.0)	0.767
Lymphadenopathy	56 (24.9)	62 (11.2)	< 0.001
Shock	10 (4.4)	5 (0.9)	0.002

Data are presented as number (%)

Abbreviations: ADIs, acquired immunodeficiency syndrome (AIDS)-defining illnesses; HIV, human immunodeficiency virus; PLWH, people living with HIV

The most common OIs in PLWH with ADIs were PJP (42.7%), talaromycosis (27.1%), pulmonary tuberculosis (14.2%), cryptococcosis (9.8%) and extra-pulmonary tuberculosis (8.9%) (Table 3). The median cluster of differentiation 4 (CD4) count (IQR) at diagnosis was 31 (17, 65), 17 (7, 30), 74 (26, 182), 24 (16, 53) and 60 (32, 142) cells/cu.mm for PJP, talaromycosis, pulmonary tuberculosis, cryptococcosis and extra-pulmonary tuberculosis, respectively (Fig. 3).

Table 3.

Opportunistic infections in people living with HIV with and without AIDS-defining illnesses

	PLWH with ADIs (N = 225)	PLWH without ADIs (N = 552)	P-value
Opportunistic infections	225 (100)	29 (5.3)	< 0.001
Oral candidiasis	90 (40.0)	28 (5.1)	< 0.001
Pneumocystis pneumonia	96 (42.7)	0 (0)	< 0.001
Talaromycosis	61 (27.1)	0 (0)	< 0.001
Pulmonary tuberculosis	32 (14.2)	0 (0)	< 0.001
Cryptococcosis	22 (9.8)	0 (0)	< 0.001
Extra-pulmonary tuberculosis	20 (8.9)	0 (0)	< 0.001
Salmonellosis	10 (4.4)	4 (0.7)	0.001
Toxoplasmosis	11 (4.9)	0 (0)	< 0.001
Esophageal candidiasis	4 (1.8)	0 (0)	0.007
Histoplasmosis	2 (0.9)	0 (0)	0.084
CMV retinitis	8 (3.6)	0 (0)	< 0.001
CMV diseases*	3 (1.3)	0 (0)	0.024
Mycobacterium avium complex infections	2 (0.9)	0 (0)	0.084
HIV-associated cancers	8 (3.6)	0 (0)	< 0.001
Others	5 (2.2)	1 (0.2)	0.009

Data are presented as number (%)

Abbreviations: ADIs, acquired immunodeficiency syndrome (AIDS)-defining illnesses; CMV, cytomegalovirus; HIV, human immunodeficiency virus; PLWH, people living with HIV

*CMV diseases include esophagitis [1], duodenitis [1], and pneumonitis [1]

Fig. 3.

Median (interquartile range, IQR) of CD4 counts at the time of diagnosis of opportunistic infections

Among the 777 individuals, PLWH with ADIs had significantly lower hemoglobin levels, white blood cell counts, lymphocyte percentages, and albumin levels. In contrast, their aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) levels were significantly higher. The median CD4 count (IQR) at diagnosis was significantly lower in PLWH with ADIs (34 (16, 83) cells/cu.mm) than in those without ADIs (293 (183, 437) cells/cu.mm). After treatment, the median CD4 count in PLWH with ADIs increased to 195 cells/cu.mm (9%) at 6 months and 257 cells/cu.mm (11%) at 12 months. In contrast, those without ADIs had a higher CD4 count after treatment, reaching 493 cells/cu.mm (21%) at 6 months and 465 cells/cu.mm (21%) at 12 months.

According to the Thailand National Guidelines on HIV/AIDS Treatment and Prevention, baseline HIV-1 RNA testing prior to cART initiation was not routinely recommended [13]; therefore, only 46 patients (5.9%) had HIV viral load measurements at the time of HIV diagnosis. In addition, follow-up viral load data were incomplete, with HIV viral load results available for 651 patients (83.8%) at 6 months and 258 patients (33.2%) at 12 months, and these measurements did not necessarily represent the same individuals over time. As a result, interpretation of viral suppression rates would be subject to under- or overestimation. We therefore decided not to present HIV viral load data in the manuscript.

With regard to hepatitis co-infection, hepatitis B surface (HBs) antigen testing was performed in all but one patient. Anti-hepatitis C virus (HCV) antibody tests were carried out on all but 8 patients (one each year from 2012 to 2018 and three in 2019). Additionally, the proportion of newly diagnosed PLWH who underwent anti-HBs and anti-hepatitis B core (HBc) antibody testing increased significantly over time (p < 0.001 and p = 0.048 for anti-HBs antibody and anti-HBc antibody, respectively) (Table 4; Fig. 4). Regarding co-infections, 80 patients (10.3%) had hepatitis B virus (HBV) infection: 33 (14.7%) in those with ADIs and 47 (8.5%) in those without ADIs. HCV infection was detected in 32 patients (4.2%). Co-infection with both HBV and HCV was detected in 5 of 769 patients (0.6%). Syphilis was identified in 109 of the 588 patients tested, defined as reactive rapid plasma reagin (RPR) with or without a reactive Treponema pallidum hemagglutination assay (TPHA). In addition, 22 patients (3.7%) had a history of syphilis, defined by a non-reactive RPR but a reactive TPHA. (Table 4).

Table 4.

Laboratory findings in newly diagnosed people living with HIV with and without AIDS-defining illnesses

Investigations	PLWH with ADIs (N = 225)	PLWH without ADIs (N = 552)	P-value
Hemoglobin level (g/dL)	10.8 (9.5, 12.2)	13.7 (12.3, 14.8)	< 0.001
White blood cells (cells/cu.mm)	5505 (4180, 8370)	6380 (5240, 7760)	0.001
Neutrophil (%)	73.3 (63.0, 80.5)	55.1 (46.0, 64.5)	< 0.001
Lymphocyte (%)	16.7 (11.4, 24.1)	32.2 (25.0, 40.5)	< 0.001
Platelets (x1000 cells/cu.mm)	252 (176, 324)	236 (198, 282)	0.206
Blood urea nitrogen (mg/dL)	11.0 (8.0, 14.0)	11 (9.0, 13.0)	0.813
Albumin (g/dL)	3.4 (2.8, 3.8)	4.4 (4.0, 4.7)	< 0.001
Aspartate aminotransferase (U/L)	41.0 (27.0, 70.0)	22.0 (18.0, 30.0)	< 0.001
Alanine aminotransferase (U/L)	26.0 (16.0, 45.0)	21.0 (14.0, 34.0)	0.004
Alkaline phosphatase (U/L)	86.0 (65.0, 125.0)	71.0 (60.0, 85.0)	< 0.001
CD4 counts at diagnosis (cells/cu.mm)	N = 225 34 (16, 83)	N = 548 293 (183, 437)	< 0.001
% CD4 at diagnosis	N = 225 4 (2, 8)	N = 550 14 (10, 19)	< 0.001
Median CD4 counts at 6 months (cells/cu.mm)	N = 179 195 (128, 254)	N = 470 493 (332, 675)	< 0.001
% CD4 at 6 months	N = 179 9 (6, 14)	N = 470 21 (15, 27)	< 0.001
CD4 counts at 12 months (cells/cu.mm)	N = 157 257 (176, 336)	N = 242 465 (295, 650)	< 0.001
% CD4 at 12 months	N = 157 11 (7, 15)	N = 242 21 (13, 26)	< 0.001
HBsAg positivity	33/225 (14.7)	47/551 (8.5)	0.013
Isolated anti-HBc positivity	24/156 (15.4)	35/412 (8.5)	0.021
Anti-HBs positivity	70/187 (37.4)	184/485 (37.9)	0.904
Anti-HCV positivity	10/222 (4.5)	22/547 (4.0)	0.842
RPR reactivity	28/221 (12.7)	93/546 (17.0)	0.155
TPHA positivity	26/171 (15.2)	97/419 (23.2)	0.034
Serum cryptococcal antigen positivity	22/217 (10.1)	0/374 (0)	< 0.001

Data are presented as median (IQR) and number (%) as appropriate

Abbreviations: ADIs, acquired immunodeficiency syndrome (AIDS)-defining illnesses; BUN, blood urea nitrogen; CMV, cytomegalovirus; HBsAg, hepatitis B surface antigen; HBc, hepatitis B core; HIV, human immunodeficiency virus; PLWH, people living with HIV; RPR, rapid plasma regain; TPHA, Treponemal pallidum hemagglutination

Fig. 4.

Percentages of newly diagnosed people living with HIV (PLWH) who got tested for anti-HBs antibody and anti-HBc antibody by year

Multivariable analysis identified age ≥ 40 years (Odds ratio (OR) 2.10, 95% confidence interval (CI) 1.31–3.37), heterosexual route of HIV transmission (OR 2.36, 95% CI 1.52–3.68), HBV co-infection defined by positive HBs antigen (OR 2.01, 95% CI 1.05–3.82), and isolated anti-HBc positivity (OR 2.04, 95% CI 1.13–3.71) as factors associated with the presence of ADIs. In contrast, each additional calendar year was associated with a reduced risk of ADIs (OR 0.92, 95% CI 0.85–0.99).

The hospitalization rate among newly diagnosed PLWH was 25.5%; 72.0% (162 patients) in those with ADIs and 6.5% (35 patients) in those without ADIs (p < 0.001). The median duration of hospitalization was also significantly longer in patients with ADIs (9 (IQR 6, 18) vs. 6 (4, 8.5) days, p = 0.002). Only one patient died during hospitalization due to Salmonella septicemia and disseminated talaromycosis, which corresponds to an in-hospital mortality rate of 0.5%.

Discussion

This study found that 29.0% of newly diagnosed PLWH presented with ADIs, representing a decline from earlier reports in Thailand, which ranged from 35 to 70% [4, 6]. This trend aligns with global efforts to improve early HIV detection and treatment [14, 15]. The prevalence of ADIs varies by region. In Ghana (2018–2019), 33.1% of newly diagnosed PLWH had OIs, with 70% classified as WHO stage III or IV [15]. In northeastern Romania (2021–2022), nearly 50% of new HIV cases presented with ADIs [14]. Together, these findings underscore the need for proactive HIV testing strategies globally, including but not limited to provider-initiated testing among individuals with sexually transmitted infections, HBV or HCV infection, or tuberculosis, as well as expanded routine HIV screening for hospitalized patients of reproductive age, to facilitate earlier diagnosis and reduce late presentation.

The majority (80%) of newly diagnosed PLWH in this study were male, which is higher than the national data (59%) [16]. Patients with ADIs were significantly older than those without ADIs. Sexual transmission was the predominant route of HIV acquisition, with heterosexual transmission more common among PLWH with ADIs and homosexual transmission more common among those without ADIs, consistent with previous findings [4–6, 10, 11]. Thailand has seen a shift in transmission patterns, with men who have sex with men (MSM) now the main risk group [4–6, 10, 11]. The overall rate of mother-to-child transmission (MTCT) has decreased significantly, from 4.6% in 2008 [17] to 1.96% in 2022 [16], with Thailand targeting a rate of < 1% by 2030 [18]. Only one case of MTCT (0.13%) was documented in this study.

Almost all PLWH with ADIs had symptoms at diagnosis, most commonly fever, weight loss, cough and mucocutaneous lesions. In those without ADIs, over half were asymptomatic, with mucocutaneous lesions, weight loss, fever and lymphadenopathy being the most common symptoms. The spectrum of opportunistic infections (OIs) varied over time and by region. In this study, the most common OIs were PJP (42.7%), talaromycosis (27.1%), pulmonary tuberculosis (14.2%), cryptococcosis (9.8%), and extrapulmonary tuberculosis (8.9%). Historical data from this hospital in 1991 showed a different distribution, with tuberculosis, cryptococcosis and talaromycosis being more common, while PJP was likely underdiagnosed due to diagnostic limitations at that time [19]. Previous studies in Bangkok identified PJP, tuberculosis, cryptococcosis and CMV retinitis as the most common OIs [4, 6]. Across Asia, tuberculosis, PJP and cryptococcosis remain the leading OIs [20]. A multicenter study in Japan, Thailand, Vietnam and the Philippines (2003–2011) highlighted regional differences: tuberculosis was the predominant OI in Hanoi, Manila, and Lampang, while PJP was more common in Nagoya [21]. Talaromycosis was found only in Lampang and Hanoi, reflecting its endemicity in northern Thailand and Vietnam [9, 19, 21, 22]. Geographic and temporal variation in ADIs likely reflects differences in regional pathogen endemicity, environmental exposure, and availability of healthcare resources for the diagnosis of OIs.

PLWH with ADIs had significantly lower hemoglobin, white blood cell count, lymphocyte, and albumin levels and higher liver enzyme abnormalities, likely due to chronic inflammation, immune suppression, and malnutrition [4]. These findings are consistent with previous Thai studies [4]. The median CD4 count at diagnosis was significantly lower in PLWH with ADIs (34 vs. 293 cells/cu.mm). Despite improvements after treatment, the CD4 counts in PLWH with ADIs remained lower at 6 and 12 months than in those without ADIs [23].

Co-infections with HBV and HCV were more common, 10.3% had HBV and 4.1% had HCV, a marked increase from previous Thai studies (7.4% HBV and 8.1% HCV in Bangkok [6], 8.7% HBV and 12.2% HCV in an Asian multicenter study) [5]. In contrast, a 2006 Thai study reported no syphilis-HIV co-infections in newly diagnosed PLWH [6], while this study found a prevalence of almost 20%. A 2022 meta-analysis from China found a 20% syphilis prevalence among PLWH [23], nearly doubling the rate reported in 2011 (9.5%) [24]. This increase in HIV-syphilis co-infection rates may be attributed to the increasing use of pre-exposure prophylaxis (PrEP) leading to decreased condom use, as well as changes in sexual behavior facilitated by online dating and mobile applications [25–27]. Testing for anti-HBs and anti-HBc is crucial for detecting occult HBV infection and assessing immune status. A study in India reported that among newly diagnosed PLWH who were HBsAg-negative but anti-HBc-positive, 10.7% had occult HBV infection, characterized by chronic low-level HBV replication in the absence of detectable HBs antigen [28]. In this study, 60% and 70% of newly diagnosed PLWH were tested for anti-HBc and anti-HBs in 2012, with a significant increase in testing rates over time. Given the importance of HBV screening, all newly diagnosed PLWH should be tested for HBs antigen, anti-HBc and anti-HBs antibodies.

Regarding factors associated with ADIs, the multivariable analysis was limited to demographic characteristics and co-infections present at the time of HIV diagnosis, including viral hepatitis and syphilis. Clinical presentations, opportunistic infection diagnoses, and laboratory abnormalities were not included in the multivariable analysis, as these variables represent manifestations of ADIs rather than independent predictors. The association between age ≥ 40 years and AIDS presentation likely reflects delayed HIV diagnosis, age-related immune decline, and reduced uptake of routine HIV screening among older adults, resulting in more advanced immunosuppression at the time of diagnosis [29–32]. Similarly, heterosexual transmission may be associated with a lower perceived risk of HIV infection, leading to delayed HIV testing and late diagnosis [29, 30, 33]. The association between HBV co-infection and AIDS presentation likely reflects shared transmission routes, prolonged undiagnosed HIV infection, and impaired immune control of HBV in the setting of advanced immunosuppression, leading to increased HBV persistence and detectability at diagnosis [34, 35]. Isolated anti-HBc positivity among patients with AIDS which represent either low-level HBV viremia or loss of protective anti-HBs antibodies [34]. In our setting, HBV DNA testing was not routinely performed to differentiate between these conditions. The latter scenario likely reflects prior HBV exposure with impaired immune control and loss of protective anti-HBs in advanced HIV-related immunosuppression, serving as a marker of delayed HIV diagnosis [36]. After adjusting for those factors, each additional calendar year was associated with a reduced risk of ADIs.

The hospitalization rate among newly diagnosed PLWH was 25.5% and was markedly higher among those with ADIs compared with those without ADIs (72.0% vs. 6.5%). In addition, patients with ADIs experienced a significant longer median hospital stay than those without ADIs (9 vs. 6 days, p = 0.002), underscoring the substantial clinical burden associated with ADIs [6]. The in-hospital mortality rate was 0.5%, which was lower than the rates reported in Bangkok (5.4%) [6] and New York (2.6%) [8].

Strengths and limitations

This study provides the first comprehensive data on newly diagnosed PLWH in northern Thailand, including baseline characteristics, symptoms, diagnoses, and laboratory tests. However, several limitations should be acknowledged. First, the retrospective design resulted in some missing data. Second, the study was conducted at a tertiary-care hospital, which may overrepresent patients with advanced or complex diseases and limit generalizability to primary-care or community settings in Thailand or to other resource-limited settings. Third, case identification relied on ICD-10 codes (B20–B24), which may have led to under-ascertainment or misclassification of newly diagnosed HIV cases, particularly among patients managed exclusively in outpatient settings; however, consistent coding practices were applied throughout the study period, reducing the likelihood of differential misclassification affecting temporal trend analyses. Consequently, public health implications should be interpreted with caution.

Conclusions

Although the prevalence of ADIs among PLWH has declined, nearly one-third of newly diagnosed individuals still present with advanced disease, highlighting persistent gaps in early HIV diagnosis. Early detection of HIV is essential to reduce the burden of ADIs, improve survival, and prevent avoidable morbidity. Proactive and systematic HIV testing in at-risk populations is therefore essential to ensure timely diagnosis and prompt initiation of cART. Expanding routine and provider-initiated HIV screening programs will not only reduce late presentation and the occurrence of ADIs, but also decrease onward transmission, yielding substantial benefits for both individual patient outcomes and public health.

Abbreviations

ADI

Acquired immunodeficiency syndrome-defining illness

AIDS

Acquired immunodeficiency syndrome

ALP

Alkaline phosphatase

ALT

Alanine aminotransferase

AST

Aspartate aminotransferase

cART

Combination antiretroviral therapy

CI

Confidence interval

CD4

Cluster of differentiation 4

CMV

Cytomegalovirus

IQR

Interquartile range

HBc

Hepatitis B core

HBs

Hepatitis B surface

HBV

Hepatitis B virus

HCV

Hepatitis C virus

HIV

Human immunodeficiency virus

MAC

Mycobacterium avium complex

MSM

Men who have sex with men

MTCT

Mother-to-child transmission

OI

Opportunistic infection

OR

Odds ratio

PJP

Pneumocystis jirovecii pneumonia

PLWH

People living with HIV

PrEP

Pre-exposure prophylaxis

RPR

Rapid plasma reagin

TPHA

Treponema pallidum hemagglutination assay

Author contributions

D.S. participated in trial design, data collection, data curation, statistical data analysis, data interpretation, and drafted the manuscript. N.W. participated in statistical data analysis. R.C. participated in trial design, data curation, statistical data analysis, data interpretation, supervision, and critically revised the manuscript for important intellectual content. All authors read and approved the final manuscript.

Funding

None.

Data availability

The datasets used and/or analyzed during the current study, excluding potentially identifying or sensitive patient information, are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

The study was conducted in accordance with the Declaration of Helsinki and was approved by the Research Ethics Committee Panel 5, Faculty of Medicine Chiang Mai University (Study Code: MED-2566-0165; Approval No. 303/2023; Approval Date: August 25, 2023). The Research Ethics Committee Panel 5, Faculty of Medicine Chiang Mai University waived the requirement for informed consent to participate because of the retrospective study design, and the data were obtained from electronic medical records and contained no identifiable patient information.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.