Chronic kidney disease (CKD) is a major health issue for HIV-positive individuals, associated with increased morbidity and mortality. Development and implementation of a risk score model for CKD would allow comparison of the risks and benefits of adding potentially nephrotoxic antiretrovirals to a treatment regimen and would identify those at greatest risk of CKD. The aims of this study were to develop a simple, externally validated, and widely applicable long-term risk score model for CKD in HIV-positive individuals that can guide decision making in clinical practice.
Methods and Findings
A total of 17,954 HIV-positive individuals from the Data Collection on Adverse Events of Anti-HIV Drugs (D:A:D) study with ≥3 estimated glomerular filtration rate (eGFR) values after 1 January 2004 were included. Baseline was defined as the first eGFR > 60 ml/min/1.73 m2 after 1 January 2004; individuals with exposure to tenofovir, atazanavir, atazanavir/ritonavir, lopinavir/ritonavir, other boosted protease inhibitors before baseline were excluded. CKD was defined as confirmed (>3 mo apart) eGFR ≤ 60 ml/min/1.73 m2. Poisson regression was used to develop a risk score, externally validated on two independent cohorts.
In the D:A:D study, 641 individuals developed CKD during 103,185 person-years of follow-up (PYFU; incidence 6.2/1,000 PYFU, 95% CI 5.7–6.7; median follow-up 6.1 y, range 0.3–9.1 y). Older age, intravenous drug use, hepatitis C coinfection, lower baseline eGFR, female gender, lower CD4 count nadir, hypertension, diabetes, and cardiovascular disease (CVD) predicted CKD. The adjusted incidence rate ratios of these nine categorical variables were scaled and summed to create the risk score. The median risk score at baseline was −2 (interquartile range –4 to 2). There was a 1:393 chance of developing CKD in the next 5 y in the low risk group (risk score < 0, 33 events), rising to 1:47 and 1:6 in the medium (risk score 0–4, 103 events) and high risk groups (risk score ≥ 5, 505 events), respectively. Number needed to harm (NNTH) at 5 y when starting unboosted atazanavir or lopinavir/ritonavir among those with a low risk score was 1,702 (95% CI 1,166–3,367); NNTH was 202 (95% CI 159–278) and 21 (95% CI 19–23), respectively, for those with a medium and high risk score. NNTH was 739 (95% CI 506–1462), 88 (95% CI 69–121), and 9 (95% CI 8–10) for those with a low, medium, and high risk score, respectively, starting tenofovir, atazanavir/ritonavir, or another boosted protease inhibitor.
The Royal Free Hospital Clinic Cohort included 2,548 individuals, of whom 94 individuals developed CKD (3.7%) during 18,376 PYFU (median follow-up 7.4 y, range 0.3–12.7 y). Of 2,013 individuals included from the SMART/ESPRIT control arms, 32 individuals developed CKD (1.6%) during 8,452 PYFU (median follow-up 4.1 y, range 0.6–8.1 y). External validation showed that the risk score predicted well in these cohorts. Limitations of this study included limited data on race and no information on proteinuria.
Both traditional and HIV-related risk factors were predictive of CKD. These factors were used to develop a risk score for CKD in HIV infection, externally validated, that has direct clinical relevance for patients and clinicians to weigh the benefits of certain antiretrovirals against the risk of CKD and to identify those at greatest risk of CKD.
About 35 million people are currently infected with HIV, the virus that causes AIDS. HIV destroys CD4 lymphocytes and other immune system cells, leaving infected individuals susceptible to other infections. HIV infection can be controlled, but not cured, using combination antiretroviral therapy (cART), and, nowadays, the life expectancy of many HIV-positive individuals is similar to that of HIV-negative people. HIV-positive individuals nevertheless experience some illnesses more frequently than HIV-negative people do. For example, up to a third of HIV-positive individuals develop chronic kidney disease (CKD), which is associated with an increased risk of cardiovascular disease and death. Persons with CKD may have an impaired effect of the filtration units in the kidneys that remove waste products and excess water from the blood to make urine, thereby leading to a reduced blood filtration rate (the estimated glomerular filtration rate [eGFR]) and waste product accumulation in the blood. Symptoms of CKD, which rarely occur until the disease is advanced, include tiredness, swollen feet, and frequent urination. Advanced stages of CKD cannot be cured, but its progression can be slowed by, for example, controlling hypertension (high blood pressure) and diabetes (two CDK risk factors) and by adopting a healthy lifestyle.
Why Was This Study Done?
The burden of CKD may increase among HIV-positive individuals as they age, and clinicians need to know which individuals are at high risk of developing CKD when choosing cART regimens for their patients. In addition, clinicians need to be able to identify those HIV-positive individuals at greatest risk of CKD so that they can monitor them for early signs of kidney disease. Some antiretroviral drugs—for example, tenofovir and atazanavir/ritonavir (a boosted protease inhibitor)—are associated with kidney damage. Clinicians may need to weigh the benefits and risks of giving such potentially nephrotoxic drugs to individuals who already have a high CKD risk. Here, the researchers develop and validate a simple, widely applicable risk score (a risk prediction model) for CKD among HIV-positive individuals and investigate the relationship between CKD and potentially nephrotoxic antiretroviral drugs among individuals with different CKD risk score profiles.
What Did the Researchers Do and Find?
To develop their CKD risk score, the researchers used clinical and demographic data collected from 17,954 HIV-positive individuals enrolled in the Data Collection on Adverse Events of Anti-HIV Drugs (D:A:D) study who had an eGFR > 60 ml/min/1.73 m2 and were not taking a potentially nephrotoxic antiretroviral at baseline. During 103,185 person-years of follow-up, 641 individuals developed CKD. Older age, intravenous drug use, hepatitis C coinfection, lower baseline eGFR, female gender, lower CD4 count nadir, hypertension, diabetes, and cardiovascular disease predicted CKD. The researchers included these nine factors in their risk score model (which is available online) and defined three risk groups: low (risk score < 0), medium (risk score 0–4), and high (risk score ≥ 5) risk of CKD development in the next five years. Specifically, there was a 1 in 393, 1 in 47, and 1 in 6 chance of developing CKD in the next five years in the low, medium, and high risk groups, respectively. Because some patients started to use potentially nephrotoxic antiretroviral drugs during follow-up, the researchers were able to use their risk score model to calculate how many patients would have to be treated with one of these drugs for an additional patient to develop CKD over five years in each risk group. This “number needed to harm” (NNTH) for patients starting treatment with tenofovir, atazanavir/ritonavir, or another boosted protease inhibitor was 739, 88, and 9 in the low, medium, and high risk groups, respectively. Finally, the researchers validated the accuracy of their risk score in two independent HIV study groups.
What Do These Findings Mean?
These findings provide a simple, validated risk score for CKD and indicate that the NNTH when starting potentially nephrotoxic antiretrovirals was low among HIV-positive individuals at the highest risk of CKD (i.e., treating just nine individuals with nephrotoxic antiretroviral drugs will likely lead to an additional case of CKD in five years). Although various aspects of the study, including the lack of data on race, limit the accuracy of these findings, these findings highlight the need for monitoring, screening, and chronic disease prevention to minimize the risk of HIV-positive individuals developing diabetes, hypertension, or cardiovascular disease, or becoming coinfected with hepatitis C, all of which contribute to the CKD risk score. Moreover, the development of a tool for estimating an individual’s five-year risk of developing CKD with or without the addition of potentially nephrotoxic antiretroviral drugs will enable clinicians and patients to weigh the benefits of certain antiretroviral drugs against the risk of CKD and make informed decisions about treatment options.
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001809.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS, summaries of recent research findings on HIV care and treatment, and personal stories about living with AIDS/HIV
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including personal stories about living with HIV/AIDS
The World Health Organization provides information on all aspects of HIV/AIDS (in several languages), including its guidelines on the use of ART for treating and preventing HIV infection
The UNAIDS World AIDS Day Report 2014 provides up-to-date information about the AIDS epidemic and efforts to halt it
The UK National Health Service Choices website provides information for patients on chronic kidney disease, including some personal stories
The US National Kidney Foundation, a not-for-profit organization, provides information about chronic kidney disease (in English and Spanish)
A tool for calculating the CDK risk score developed in this study is available
Additional information about the D:A:D study is available
Amanda Mocroft and colleagues develop and validate a model for determining risk of developing chronic kidney disease for individuals with HIV if treated with different antiretroviral therapies.