Dolutegravir/Lamivudine Is Noninferior to Continuing Dolutegravir- and Non-Dolutegravir-Based Triple-Drug Antiretroviral Therapy in Virologically Suppressed People With Human Immunodeficiency Virus: DUALING Prospective Nationwide Matched Cohort Study.

Background: Confirming the efficacy of dolutegravir/lamivudine in clinical practice solidifies recommendations on its use. Methods: Prospective cohort study (DUALING) in 24 human immunodeficiency virus (HIV) treatment centers in the Netherlands. HIV RNA-suppressed cases were on triple-drug antiretroviral regimens without prior virological failure or resistance and started dolutegravir/lamivudine. Cases were 1:2 matched to controls on triple-drug antiretroviral regimens by the use of dolutegravir-based regimens, age, sex, transmission route, CD4+ T-cell nadir, and HIV RNA zenith. The primary endpoint was the treatment failure rate in cases versus controls at 1 year by intention-to-treat and on-treatment analyses with 5% noninferiority margin. Results: The 2040 participants were 680 cases and 1380 controls. Treatment failure in the 390 dolutegravir-based cases versus controls occurred in 8.72% and 12.50% (difference: -3.78% [95% confidence interval {CI}, -7.49% to .08%]) by intention-to-treat and 1.39% and 0.80% (difference: 0.59% [95% CI, -.80% to 1.98%]) by on-treatment analyses. The treatment failure risk in 290 non-dolutegravir-based cases was also noninferior to controls. Antiretroviral regimen modifications unrelated to virological failure explained the higher treatment failure rate by intention-to-treat. A shorter time on triple-drug antiretroviral therapy and being of non-Western origin was associated with treatment failure. Treatment failure, defined as 2 consecutive HIV RNA >50 copies/mL, occurred in 4 cases and 5 controls but without genotypic resistance detected. Viral blips occured comparable in cases and controls but cases gained more weight, especially when tenofovir-based regimens were discontinued. Conclusions: In routine care, dolutegravir/lamivudine was noninferior to continuing triple-drug antiretroviral regimens after 1 year, supporting the use of dolutegravir/lamivudine in clinical practice. Clinical Trials Registration: NCT04707326.

Switching to Doravirine in cART-Experienced Patients: An Effective and Highly Tolerated Option With Substantial Cost Savings.

BACKGROUND: Doravirine is a non-nucleoside reverse transcriptase inhibitor with demonstrated efficacy as a third agent in treatment-naive and treatment-experienced people living with HIV (PLWH) in registration studies. However, limited real-world data are available. METHODS: By searching electronic health care records, PLWH using doravirine-based regimens were selected with at least 1 year of follow-up after their first prescription. All stable PLWH who were switched to a doravirine-based regimen were included in the analysis. The primary outcome was the durability of a doravirine-based regimen 1 year after prescription. Reasons for stopping were also collected. Secondary outcomes for PLWH continuing a doravirine-based regimen after 1 year were routine laboratory assessment, body mass index, and differences in medication costs compared with their previous cART. RESULTS: A total of 687 patients (92% men) were included from September 2019 to August 2022: 97.7% switched to doravirine/tenofovir/lamivudine (DOR/TDF/3TC). After 1 year, 94/687 (13.6%) PLWH stopped this therapy. The main reason for discontinuation was patient-reported adverse events in 70/687 (10.2%). Medical reasons for discontinuation included increased alanine tranaminase levels in 6/687 (0.9%), decreased estimated glomerular filtration rate in 3/687 (0.4%), and precautions after diagnosis of osteoporosis in 2/687 (0.3%) patients. Virologic failure occurred in 4/687 cases (0.6%), and 1 case demonstrated resistance mutations. The secondary outcomes demonstrated a statistically significant increase in alanine tranaminase levels and decrease in LDL-c levels. The switch to a doravirine-based regimen in the Netherlands reduced medication costs by 27%. CONCLUSIONS: This study demonstrated that switching to a doravirine-based regimen, mostly DOR/TDF/3TC, was highly effective and generally well tolerated, with substantial cost savings.

Persistent Transmission of HCV among Men Who Have Sex with Men despite Widespread Screening and Treatment with Direct-Acting Antivirals.

BACKGROUND: In the Netherlands, unrestricted access to direct-acting antivirals (DAAs) halved the incidence of acute hepatitis C virus (HCV) infections among HIV-infected men who have sex with men (MSM). To develop strategies that can further reduce the spread of HCV, it is important to understand the transmission dynamics of HCV. We used phylogenetic analysis of a dense sample of MSM to provide insight into the impact of unrestricted access to DAAs on HCV transmission in the Netherlands and in Belgium. METHODS: We included 89 MSM that were recently infected with HCV genotype 1a in ten Dutch and one Belgian HIV treatment centers. Sequences were generated using next gene sequencing and Sanger sequencing. Maximum likelihood phylogenetic analysis (general time reversible model) was performed on concatenated NS5A and NS5B sequences and a reference set of 389 highly similar control sequences selected from GenBank. A cluster was based on a minimum bootstrap support of 90% and a 3% genetic distance threshold. RESULTS: We found that 78 (88%) of individuals were part of seven major clusters. All clusters included individuals from across the study region, however, different cities were part of different clusters. In three clusters, HIV-negative MSM clustered with sequences from HIV-positive MSM. All clusters that were observed before the introduction of DAAs persisted after unrestricted access to DAAs became available. CONCLUSION: Recently acquired HCV infections among MSM in the Netherlands and Belgium are strongly clustered and therefore highly suitable for targeted prevention strategies, such as contact tracing and partner notification. Importantly, despite an HCV incidence reduction after high DAA uptake and continuously monitoring, HCV transmission persisted in the same clusters.

[Peritoneal tuberculosis in a postmenopausal woman with progressive ascites]. / Peritoneale tuberculose.

BACKGROUND: The non-specific symptomatology in peritoneal tuberculosis often results in a delay in the diagnosis. Due to clinical overlap symptoms may be confused with metastatic ovarian carcinoma. This can lead to delayed treatment, unnecessary surgical interventions and a deteriorated prognosis. CASE DESCRIPTION: A 75-year-old female of Moroccan descent was referred to the gastroenterology department with increasing ascites and weight loss. Based on the clinical picture metastatic ovarian cancer was suspected. However, repeatedly no malignant cells were found in both ascitic fluid and tissue biopsies. Peritoneal tuberculosis was considered and ovarian malignancy could not be excluded. A diagnostic laparoscopyand biopsy was considered necessary. The laparoscopic view was pathognomic for tuberculosis after which antituberculosis treatment was started with good result. CONCLUSION: Peritoneal tuberculosis should be included in the differential diagnosis in women from endemic areas with symptoms of abdominal pain, ascites, weight loss and/or increased CA-125. Laparoscopy should be considered if less invasive tests are inconclusive about the diagnosis.

Role of Self-Stigma in Pathways from HIV-Related Stigma to Quality of Life Among People Living with HIV.

This study examined the relationships between perceived public stigma, experienced stigma, and quality of life in people living with HIV (PLHIV), and whether self-stigma mediates these relationships. Cross-sectional data were analyzed from 1704 PLHIV in care at OLVG hospital in the Netherlands. We measured different types of stigma (perceived public stigma, experienced stigma, and self-stigma), and various quality-of-life outcomes (disclosure concerns, depression, anxiety, sexual problems, sleeping difficulties, self-esteem, general health, and social support). Structural equation modeling was used to test the paths from different types of stigma to quality-of-life outcomes. All direct effects of self-stigma on quality-of-life outcomes were significant. The final mediation model showed that the effects of both perceived public and experienced stigma on quality-of-life outcomes were mediated by self-stigma. These findings highlight the importance of addressing self-stigma in PLHIV, and call for (psychosocial) interventions that reduce the harmful effects of HIV-related stigma.

Evaluation of the Hepatitis C Testing Strategy for Human Immunodeficiency Virus-Positive Men Who Have Sex With Men at the Sexually Transmitted Infections Outpatient Clinic of Amsterdam, the Netherlands.

INTRODUCTION: As the incidence of hepatitis C virus (HCV) infections remains high among human immunodeficiency virus (HIV)-positive men who have sex with men (MSM) an HCV testing strategy was introduced at the sexually transmitted infections (STI) clinic in Amsterdam in 2017. We aimed to evaluate this HCV testing strategy. METHODS: The HIV-positive MSM and transgender women (TGW) were eligible for HCV testing (anti-HCV and HCV ribonucleic acid) at the STI clinic if they did not visit their HIV clinician in the 3 months before the consultation and had not been tested for HCV at the STI clinic in the previous 6 months. All eligible individuals were administered the 6 questions on risk behavior of the HCV-MSM observational study of acute infection with hepatitis C (MOSAIC) risk score; a risk score of 2 or greater made a person eligible for testing. RESULTS: From February 2017 through June 2018, 1015 HIV-positive MSM and TGW were eligible for HCV testing in 1295 consultations. Eleven active HCV infections (HCV ribonucleic acid positive) were newly diagnosed (positivity rate, 0.9%; 95% confidence interval [CI], 0.4-1.5%). Sensitivity and specificity of the HCV-MOSAIC score for newly diagnosed active HCV infections were 80.0% (95% CI, 49.0-94.3%) and 53.7% (95% CI, 50.8-56.5%), respectively. If an HCV-MOSAIC score of 2 or greater were used to determine whom to test, 46.6% of individuals currently tested for HCV would be eligible for testing. CONCLUSIONS: Using the new HCV testing strategy, HCV testing was done in 1295 consultations with HIV-positive MSM and TGW in 17 months. We newly diagnosed 11 active HCV infections. The HCV-MOSAIC risk score could reduce the number of tests needed, but some active HCV infections will be missed.

Transmission of NS5A-Inhibitor Resistance-Associated Substitutions Among Men Who Have Sex With Men Recently Infected with Hepatitis C Virus Genotype 1a.

The transmission of direct-acting antiviral resistance-associated substitutions (RAS) could hamper hepatitis C virus (HCV) cure rates and elimination efforts. A phylogenetic analysis of 87 men who have sex with men recently infected with HCV genotype 1a placed one-third (28/87) in a large cluster, in which 96% harbored NS5A M28V RAS.

Treatment of acute hepatitis C genotypes 1 and 4 with 8 weeks of grazoprevir plus elbasvir (DAHHS2): an open-label, multicentre, single-arm, phase 3b trial.

BACKGROUND: Direct-acting antivirals effectively treat chronic hepatitis C virus (HCV) infection but there is a paucity of data on their efficacy for acute HCV, when immediate treatment could prevent onward transmission. We assessed the efficacy of grazoprevir plus elbasvir treatment in acute HCV infection and investigated whether treatment can be shortened during the acute phase of HCV infection. METHODS: The Dutch Acute HCV in HIV study number 2 (DAHHS2) study was a single-arm, open-label, multicentre, phase 3b trial. Adult patients (≥18 years) with acute HCV genotype 1 or 4 infection (duration of infection 26 weeks or less, according to presumed day of infection) were recruited at 15 HIV outpatient clinics in the Netherlands and Belgium. All patients were treated with 8 weeks of grazoprevir 100 mg plus elbasvir 50 mg administered as one oral fixed drug combination tablet once daily. The primary efficacy endpoint was sustained virological response at 12 weeks after the end of treatment (SVR12; HCV RNA <15 IU/mL) in all patients who started treatment. Reinfection with a different HCV virus was not considered treatment failure in the primary analysis. This trial is registered with ClinicalTrials.gov, number NCT02600325. FINDINGS: Between Feb 15, 2016, and March 2, 2018, we assessed 146 patients with a recently acquired HCV infection for eligibility, of whom 86 were enrolled and 80 initiated therapy, all within 6 months after infection. All patients who initiated treatment completed treatment and no patients were lost to follow-up. 79 (99%, 95% CI 93-100) of 80 patients achieved SVR12. All 14 patients who were infected with a virus carrying a clinically significant polymorphism in NS5A were cured. If reinfections were considered treatment failures, 75 (94%, 86-98) of 80 patients achieved SVR12. Two serious adverse events not considered related to the treatment were reported (traumatic rectal bleeding and low back surgery). The most common adverse event was a new sexually transmitted infection (19 [24%] of 80 patients). The most common reported possibly drug-related adverse events were fatigue (11 [14%] patients), headache (seven [9%] patients), insomnia (seven [9%] patients), mood changes (five [6%] patients), dyspepsia (five [6%] patients), concentration impairment (four [5%] patients), and dizziness (4 [5%] patients), all of which were regarded as mild by the treating physician. No adverse events led to study drug discontinuation. INTERPRETATION: 8 weeks of grazoprevir plus elbasvir was highly effective for the treatment of acute HCV genotype 1 or 4 infection. The ability to treat acute HCV immediately after diagnosis might help physicians to reach the WHO goal of HCV elimination by 2030. FUNDING: Merck Sharp and Dohme and Health-Holland.

Objective and Subjective Improvement of Cognition After Discontinuing Efavirenz in Asymptomatic Patients: A Randomized Controlled Trial.

BACKGROUND: Efavirenz is well known for its clinical cognitive side effects. Even asymptomatic patients who switch for other reasons than neurocognitive complaints have reported a subjective improvement in cognitive functioning after discontinuing efavirenz. The aim of this study was to assess the effect on cognition of switching Atripla (TDF/FTC/EFV) to Eviplera (TDF/FTC/RPV), hypothesizing an improvement when discontinuing efavirenz. SETTING: A randomized controlled design with a highly comparable comparator drug was used to minimize bias and to differentiate drug versus learning effects. An extensive sensitive neuropsychological assessment (NPA) was used to detect subtle changes. METHODS: Virologically suppressed, cognitively asymptomatic male HIV-infected patients on Atripla were included and randomized (2:1) to switch to Eviplera (switch group) or continue on Atripla (control group) for 12 weeks. At baseline and week 12, patients underwent an extensive NPA. RESULTS: Fourteen control and 34 switch subjects completed the study. There were no differences at baseline. Group analysis demonstrated a significantly better improvement for the switch group on the domains attention (P = 0.041) and speed of information processing (P = 0.014). Normative comparison analyses showed that 5 of the 34 patients who switched (15%) improved on NPA score as compared to the control group. Interestingly, subjective improvement after discontinuing efavirenz made 74% of the switch group chose for a regime without efavirenz after study completion. CONCLUSIONS: Switching from Atripla to Eviplera resulted in objective cognitive improvement on the group level in cognitively asymptomatic patients. Discrepancies in objective and subjective cognitive complaints make it challenging to identify patients who would benefit from discontinuing efavirenz.

Host Cell Deoxyribonucleic Acid Methylation Markers for the Detection of High-grade Anal Intraepithelial Neoplasia and Anal Cancer.

BACKGROUND: High-grade anal intraepithelial neoplasia (AIN2/3; HGAIN) is highly prevalent in human immunodeficiency virus positive (HIV+) men who have sex with men (MSM), but only a minority will eventually progress to cancer. Currently, the cancer risk cannot be established, and therefore all HGAIN is treated, resulting in overtreatment. We assessed host cell deoxyribonucleic acid (DNA) methylation markers for detecting HGAIN and anal cancer. METHODS: Tissue samples of HIV+ men with anal cancer (n = 26), AIN3 (n = 24), AIN2 (n = 42), AIN1 (n = 22) and HIV+ male controls (n = 34) were analyzed for methylation of 9 genes using quantitative methylation-specific polymerase chain reaction. Univariable and least absolute shrinkage and selection operator logistic regression, followed by leave-one-out cross-validation, were used to determine the performance for AIN3 and cancer detection. RESULTS: Methylation of all genes increased significantly with increasing severity of disease (P < 2 × 10-6). HGAIN samples revealed heterogeneous methylation patterns, with a subset resembling cancer. Four genes (ASCL1, SST, ZIC1,ZNF582) showed remarkable performance for AIN3 and anal cancer detection (area under the curve [AUC] > 0.85). ZNF582 (AUC = 0.89), detected all cancers and 54% of AIN3 at 93% specificity. Slightly better performance (AUC = 0.90) was obtained using a 5-marker panel. CONCLUSIONS: DNA methylation is associated with anal carcinogenesis. A marker panel that includes ZNF582 identifies anal cancer and HGAIN with a cancer-like methylation pattern, warrantingvalidation studies to verify its potential for screening and management of HIV+ MSM at risk for anal cancer.

The effect of switching protease inhibitors to raltegravir on endothelial function, in HIV-infected patients.

Objective Lipid management is one of the cornerstones of cardiovascular risk reduction. Treatment of HIV infection with protease inhibitors (PIs) may cause dyslipidaemia, whilst the integrase inhibitor raltegravir (RAL) has a relatively favorable effect on plasma lipids. We examined the effect of switching from PIs to RAL on endothelial function, and its effect on immunological and inflammatory parameters. Methods We performed a 16-week open-label prospective crossover study: 8 weeks intervention (switch PIs to RAL) and 8 weeks control (unchanged cART regimen). Flow-mediated dilatation (FMD), inflammatory plasma, and cellular markers of immune activation were measured at weeks 0, 8, and 16. Results Study participants (n = 22) with a median age of 50 years (IQR 42-60) and known HIV infection of 6.5 years (IQR 5.0-17.3) were on stable cART with undetectable HIV viral loads. After 8 weeks of RAL therapy, a reduction in FMD of -0.81% was seen, compared to +0.54% control (pairwise, p = 0.051), while fasting total cholesterol (-17% versus +10%; p < 0.001), LDL cholesterol (-21% versus -3%; p = 0.026), and triglycerides (-41% versus +18%; p = 0.001) significantly decreased during RAL therapy compared to the control. Furthermore, a relation between the change in percentage of B-1 cells and the change in FMD was found (ß 0.40, 95%CI 0.16; 0.64, p = 0.005) during treatment with RAL. Finally, during RAL therapy, 27% of the patients experienced an increased ALT rise. Conclusions We present an overall negative study, where switching from PIs to RAL slightly reduced the endothelial function while decreasing plasma lipids, thus possibly decreasing the CVD risk in the long term. A transient elevation of ALT was seen upon switch to RAL.

Declining Hepatitis C Virus (HCV) Incidence in Dutch Human Immunodeficiency Virus-Positive Men Who Have Sex With Men After Unrestricted Access to HCV Therapy.

Background: Direct-acting antivirals (DAAa) cure hepatitis C virus (HCV) infections in 95% of infected patients. Modeling studies predict that universal HCV treatment will lead to a decrease in the incidence of new infections but real-life data are lacking. The incidence of HCV among Dutch human immunodeficiency virus (HIV)-positive men who have sex with men (MSM) has been high for >10 years. In 2015 DAAs became available to all Dutch HCV patients and resulted in a rapid treatment uptake in HIV-positive MSM. We assessed whether this uptake was followed by a decrease in the incidence of HCV infections. Methods: Two prospective studies of treatment for acute HCV infection enrolled patients in 17 Dutch HIV centers, having 76% of the total HIV-positive MSM population in care in the Netherlands. Patients were recruited in 2014 and 2016, the years before and after unrestricted DAA availability. We compared the HCV incidence in both years. Results: The incidence of acute HCV infection decreased from 93 infections during 8290 person-years of follow-up (PYFU) in 2014 (11.2/1000 PYFU; 95% confidence interval [CI], 9.1-13.7) to 49 during 8961 PYFU in 2016 (5.5/1000 PYFU; 4.1-7.2). The incidence rate ratio of 2016 compared with 2014 was 0.49 (95% CI, .35-.69). Simultaneously, a significant increase in the percentage positive syphilis (+2.2%) and gonorrhea (+2.8%) tests in HIV-positive MSM was observed at sexual health clinics across the Netherlands and contradicts a decrease in risk behavior as an alternative explanation. Conclusions: Unrestricted DAA availability in the Netherlands was followed by a 51% decrease in acute HCV infections among HIV-positive MSM.

Intolerance of dolutegravir-containing combination antiretroviral therapy regimens in real-life clinical practice.

OBJECTIVE: Dolutegravir (DGV) is one of the preferred antiretroviral agents in first-line combination antiretroviral therapy (cART). Though considered to be a well tolerated drug, we aimed to determine the actual rate, timing and detailed motivation of stopping DGV in a real-life clinical setting. DESIGN: A cohort study including all patients who started DGV in two HIV treatment centers in The Netherlands. METHODS: All cART-naïve and cART-experienced patients who had started DGV were identified from the institutional HIV databases. Clinical data, including motivation and timing of discontinuation of DGV, were extracted from the patient files. Factors that potentially influenced discontinuation of DGV were compared between patients who stopped or continued DGV by multivariate and Kaplan-Meier analyses. RESULTS: In total, 556 patients were included, of whom 102 (18.4%) were cART-naïve at initiation of DGV. Median follow-up time was 225 days. Overall, in 85 patients (15.3%), DGV was stopped. In 76 patients (13.7%), this was due to intolerability. Insomnia and sleep disturbance (5.6%), gastrointestinal complaints (4.3%) and neuropsychiatric symptoms such as anxiety, psychosis and depression (4.3%) were the predominant reasons for switching DGV. In regimens that included abacavir, DGV was switched more frequently (adjusted relative risk 1.92, 95% confidence interval 1.09-3.38, P log-rank 0.01). No virologic failures were observed. CONCLUSION: A relatively high rate of preliminary discontinuation of DGV due to intolerability was detected in our patient population. In particular, DGV was stopped more frequently if the regimen included abacavir. Multiple factors may explain these unexpected postmarketing observations, which warrant further investigation.

The Effect of Rosuvastatin on Markers of Immune Activation in Treatment-Naive Human Immunodeficiency Virus-Patients.

Background. Immune activation has been implicated in the excess mortality in human immunodeficiency virus (HIV)-infected patients, due to cardiovascular diseases and malignancies. Statins may modulate this immune activation. We assessed the capacity of rosuvastatin to mitigate immune activation in treatment-naive HIV-infected patients. Methods. In a randomized double-blind placebo-controlled crossover study, we explored the effects of 8 weeks of rosuvastatin 20 mg in treatment-naive male HIV-infected patients (n = 28) on immune activation markers: neopterin, soluble Toll-like receptor (TLR)2, sTLR4, interleukin (IL)-6, IL-1Ra, IL-18, d-dimer, highly sensitive C-reactive protein, and CD38 and/or human leukocyte antigen-DR expression on T cells. Baseline data were compared with healthy male controls (n = 10). Furthermore, the effects of rosuvastatin on HIV-1 RNA, CD4/CD8 T-cell count, and low-density lipoprotein cholesterol were examined and side effects were registered. Results. T-cell activation levels were higher in patients than in controls. Patients had higher levels of circulating IL-18, sTLR2, and neopterin (all P < .01). Twenty patients completed the study. Rosuvastatin increased the CD4/CD8 T-cell ratio (P = .02). No effect on other markers was found. Conclusions. Patients infected with HIV had higher levels of circulating neopterin, IL-18, sTLR2, and T-cell activation markers. Rosuvastatin had a small but significant positive effect on CD4/CD8 T-cell ratio, but no influence on other markers of T-cell activation and innate immunity was identified (The Netherlands National Trial Register [NTR] NTR 2349, http://www.trialregister.nl/trialreg/index.asp).

Boceprevir, peginterferon and ribavirin for acute hepatitis C in HIV infected patients.

BACKGROUND & AIMS: Acute hepatitis C virus infections (AHCV) are prevalent among HIV positive men having sex with men and generally treated with pegylated interferon-alpha (PegIFN) and ribavirin (RBV) during 24weeks. The addition of a protease inhibitor could shorten therapy without loss of efficacy. METHODS: We performed an open-label, single arm study to investigate the efficacy and safety of a 12-week course of boceprevir, PegIFN and RBV for AHCV genotype 1 infections in 10 Dutch HIV treatment centers. The primary endpoint of the study was achievement of sustained virological response rate at week 12 (SVR12) in patients reaching a rapid viral response at week 4 (RVR4) and SVR12 in the intent to treat (ITT) entire study population was the most relevant secondary endpoint. RESULTS: One hundred twenty-seven AHCV patients were screened in 16 months, of which 65 AHCV genotype 1 patients were included. After spontaneous clearance in six patients and withdrawal before treatment initiation in two, 57 started therapy within 26 weeks after infection. RVR4 rate was 72%. SVR12 rate was 100% in the RVR4 group. SVR12 rate in the ITT group was 86% and comparable to the SVR12 rate of 84% in 73 historical controls treated for 24 weeks with PegIFN and RBV in the same study centers. CONCLUSION: With the addition of boceprevir to PegIFN and RBV, treatment duration of AHCV genotype 1 can be reduced to 12 weeks without loss of efficacy. Given the high drug costs and limited availability of interferon-free regimens, boceprevir PegIFN and RBV can be a considered a valid treatment option for AHCV. ClinicalTrials.gov, number NCT01912495.

Cross-reactivity between darunavir and trimethoprim-sulfamethoxazole in HIV-infected patients.

OBJECTIVE: Both darunavir (DRV) and trimethoprim-sulfamethoxazole (TMP-SMX) carry a sulfonamide moiety and a warning for this cross-reactivity is given in the label of DRV. The aim of this study was to investigate the potential cross-reactivity between both drugs. DESIGN: Retrospective cohort study with a nested case-control study. METHODS: HIV-infected patients that received DRV-containing antiretroviral therapy at any time during the period of their HIV infection were included. Patients with no history of TMP-SMX use were excluded. The incidence of a DRV allergy, according to the Naranjo probability scale, was investigated in patients with an allergy to TMP-SMX compared with those without such an allergy. In order to identify possible risk factors associated with a DRV allergy among patients allergic to TMP-SMX, a nested case-control study was subsequently performed. RESULTS: A total of 405 patients were included, of whom 79 (17.5%) had a history of allergy to TMP-SMX. A DRV allergy was seen in four patients (5.1%) with a TMP-SMX allergy compared with four (1.2%) without a TMP-SMX allergy (P = 0.05). Patients with a TMP-SMX allergy were at higher risk for a DRV allergy (odds ratio 4.29; 95% confidence interval, 1.05-17.56). No additional risk factors for a DRV allergy among patients allergic to TMP-SMX were identified in the nested case-control study. CONCLUSION: Although DRV allergy is uncommon, making cross-reactivity with TMP-SMX a rare clinical problem, it appears to exist more often in the background of a TMP-SMX allergy.