The prevalence of anemia among HIV-infected adults in Africa is alarmingly high. Estimates range from 10% to 30%, depending on the hemoglobin (Hb) thresholds used and populations studied.1–4 Limited data are available regarding the commonest causes for anemia in these settings; however, they likely include drug toxicities, malaria, nutritional deficiencies, vitamin B12 deficiency, and various opportunistic infections.5
The association between an individual's Hb concentration at time of antiretroviral therapy (ART) initiation and treatment response is well documented. Numerous studies have shown low Hb to be a strong predictor of compromised clinical outcomes.3,6–11 After ART initiation, average Hb concentrations increase and anemia incidence decreases,4 trends that are at least partially dependent on the drug combinations prescribed.1,12 Recent findings from industrialized countries also suggest that changes in Hb concentrations at 6 months post-ART initiation may be associated with subsequent mortality.7 It is unknown, however, whether these observations can be extended to African populations. Given the high prevalence and varied etiologies of anemia in the region—alongside the great need for ART—the answer to this question could have important implications for optimized HIV care.
In this report, we examined the impact of early Hb change (ie, within the first 6 months) on subsequent mortality. We analyzed data from a programmatic cohort of patients receiving HIV care and treatment in Lusaka, Zambia. This program and the care it provides have been described previously.3,13 Since program inception, first-line regimens have consisted of a nonnucleoside reverse transcriptase inhibitor (nevirapine or efavirenz) combined with 2 nucleoside reverse transcriptase inhibitors [lamivudine and either zidovudine (ZDV) or stavudine]. Tenofovir and emtricitabine were introduced as alternative nucleotide reverse transcriptase inhibitors in July 2007.14 The decision to start patients on ZDV, stavudine, or tenofovir has historically been based on national guidelines, with tenofovir being recommended as first choice for most patients since 2009. We note 2 exceptions due to medical contraindications: Hb less than 10 g/dL (for ZDV) and creatinine clearance less than 50 mL/min (for tenofovir).
Our analysis cohort comprised treatment-naive HIV-infected adults (≥16 years) who initiated ART across 18 Lusaka sites between May 1, 2004, and April 30, 2010. We excluded patients who were not on treatment for at least 6 months; initiated or switched to a regimen containing a protease inhibitor (ie, second-line regimen) before 6 months; or had a missing Hb measurement at either ART initiation or 6 months into treatment.
Based on the 2004 Division of AIDS toxicity grading scale for HIV-positive adults, Hb values were categorized as normal (>10.0 g/dL), mild anemia (8.5–10.0 g/dL), or moderate and severe anemia (<8.5 g/dL).15 Our main exposure of interest was Hb concentrations at 6 months after ART initiation. To allow for potential effect modification, we stratified our analysis by baseline Hb measurements as well. We used Cox proportional hazard models to determine associations with death after the initial 6-month window. Patients with Hb measurements above >10.0 g/dL at ART initiation and 6 months follow-up were designated as the reference group. Our primary analysis was restricted to the cohort of patients with complete data for all variables of interest. Multivariate models were adjusted for age, sex, baseline CD4+ cell count, baseline clinical WHO staging, tuberculosis status, baseline ART regimen, and adherence based on a medication possession ratio at 6 months.16 In a secondary analysis, we used a multiple imputation approach to replace missing values. Separate multivariate Cox proportional hazards regression models were analyzed for each imputed dataset, and results were combined to obtain hazard ratios and corresponding 95% confidence intervals (CIs).
In a subset analysis, patients with Hb <10.0 g/dL and a documented mean corpuscular volume at 6 months were further classified as having microcytic (<80 fL), normocytic (80–100 fL), or macrocytic anemia (>100 fL). We again used a multivariate Cox proportional hazards model to determine associations with death. Patients with normocytic anemia were designated as the reference group in this secondary analysis.
Patient data available as of October 31, 2010, were considered. All analyses were performed using SAS version 9.1 (SAS Institute, Cary, NC). Use of these observational data was approved by the institutional review boards of the University of Zambia (Lusaka, Zambia) and the University of Alabama at Birmingham (Birmingham, AL).
Between May 1, 2004, and April 30, 2010, 73,016 HIV-infected adults initiated ART across participating Lusaka sites. By 6 months, 5272 (7.2%) patients had died, 8628 (11.8%) were lost to follow-up, and 357 (0.5%) initiated second-line therapy. Of the remaining 58,759 patients, 40,410 (68.8%) had Hb measurements at both baseline and 6 months and were thus included in our analysis. Compared with those included in this analysis, patients with missing baseline and/or 6-month Hb measurement had a lower median baseline CD4 count (140 vs. 146 cells/uL; P < 0.01) and were less likely to demonstrate ≥95% ART adherence over the first 6 months of treatment (63.3% vs. 73.7%; P < 0.01). We noted statistical differences in age, sex, body mass index, clinical staging, and initial ART regimen between patients included and excluded from the analysis; however, they were not thought to be clinically meaningful (see Table, Supplemental Digital Content 1, http://links.lww.com/QAI/A334).
In the analysis cohort, median follow-up was 22 months (IQR: 9–37) beyond the initial 6-month window. Post 6-month mortality was 1.59 deaths per 100 person-years (95% CI: 1.51 to 1.67). The median Hb at treatment initiation was 11.1 g/dL (IQR: 9.7–12.5). Overall, 28,131 (69.6%) had Hb >10 mg/dL; 8121 (20.1%) were mildly anemic; and 4158 (10.3%) were moderately or severely anemic. After 6 months of ART, the median Hb increased to 12.3 g/dL (IQR: 11.2–13.4), and the overall proportions with mild anemia (n = 3,030; 7.5%) or moderate to severe anemia (n = 1,117; 2.8%) had decreased.
Regardless of their baseline Hb concentration, patients with anemia at 6 months had consistently higher hazards for death compared with those with 6-month Hb >10.0 g/dL in our primary analysis (P < 0.01; Fig. 1). Moderate or severe anemia at 6 months was associated with a 4.5-fold (95% CI: 3.3 to 6.3) increase in hazard of death when compared with patients with normal Hb concentrations at 6 months. The hazard for mildly anemic patients at 6 months was also higher compared with patients with normal Hb concentrations [adjusted hazard ratio (AHR): 2.5; 95% CI: 1.9 to 3.1]. Among the 9 subcategories of our stratified analysis, the 3 subcategories containing patients with a 6-month Hb measurement less than 8.5 g/dL had the highest estimated hazard for death (Table 1).
We then conducted a secondary analysis where missing values were replaced using a multiple imputation approach. We found that moderate or severe anemia at 6 months (AHR: 3.8; 95% CI: 3.2 to 4.6) and mild anemia at 6 months (AHR: 2.1; 95% CI: 1.8 to 2.5) were consistently associated with increased in hazard of death compared with patients with normal Hb concentrations at 6 months.
Of the 4147 patients diagnosed with anemia at 6 months, a 6-month mean corpuscular volume measurement was available for 2769 (66.8%). Among these patients, 1314 (47.5%) had normocytic anemia; 804 had (29.0%) microcytic anemia; and 651 (23.5%) had macrocytic anemia. Macrocytic anemia was associated with a 1.3-fold (95% CI: 0.9 to 1.8) increased hazard for death when compared to normocytic anemia. Patients with microcytic anemia seemed to have a decreased hazard for death (AHR: 0.7; 95% CI: 0.5 to 1.1). Neither, however, reached statistical significance.
In this large African cohort, anemia detected 6 months after ART initiation was associated with higher risk for death, regardless of the baseline Hb measurement. We demonstrated elevated risk for death among patients who either develop anemia over the first 6 months of HIV treatment or have worsening disease over that window period. Similar trends have been observed among developed world cohorts.7 However, ours is the first to assess this relationship in an African setting, where the incidence and causes of anemia may differ greatly. These results reinforce the importance of continued Hb monitoring after initiation of ART, regardless of the regimen dispensed.
The association between low Hb concentrations at time of ART initiation and poor clinical outcomes among HIV-infected patients is well documented. In an analysis of 4 sub-Saharan African cohorts, patients with severe anemia had a nearly 4-fold higher risk of death in the first year of treatment compared with patients with no anemia.9 Similar findings have been shown in separate studies across Zambia,3 South Africa,11 Senegal,6 and Tanzania.8 To our knowledge, however, none have investigated postinitiation Hb concentrations and their relationship to subsequent mortality in resource-constrained settings.
Although ART has been shown to generally improve Hb levels,4 certain agents may have the opposite effect. Known side effects of ZDV, for example, include myelosuppression and macrocytic anemia. Although ZDV is commonly prescribed in our setting, our findings suggest that the incidence of anemia was not driven solely by unrecognized ZDV-related drug toxicity. Only 24% of all anemic patients at 6 months post-initiation had macrocytic anemia. It is important to note, however, that macrocytic anemia did seem to be associated with elevated risk for mortality, even if it did not meet predefined standards for statistical significance.
We recognize that the strong association between 6-month Hb concentrations and mortality does not imply a causal relationship. It is possible that low Hb may only serve as marker for other underlying health conditions, ones that will ultimately be responsible for subsequent death. In Malawi, for example, Lewis et al17 found that HIV-positive patients had higher incidences of serious but treatable conditions such as tuberculosis (38% vs. 14%) and bacteraemia (24% vs. 9%) compared with those who were HIV negative. Rigorously conducted clinical trials are needed to determine whether proper diagnosis and treatment of anemia can lead to improved patient outcomes. Simple interventions such as vitamin supplementation (eg, B12, folic acid) and/or antibiotic treatment for underlying infections could be used to prevent certain anemia types, particularly in settings where malnutrition and food insecurity are prevalent. Resources for more comprehensive laboratory evaluations could also improve patient outcomes because treatment for anemia in Zambia is often empiric and may not accurately address the underlying cause of disease.
The key strength of this study was the availability of treatment outcomes and routinely collected Hb measurements for a large number of Zambian adults on ART. Even though the overall mortality rate after 6 months of HIV treatment was 1.59 deaths per 100 person-years, we were able to compare outcomes for different anemia classifications with precision. We also recognize several limitations. First, nearly one-third of patients had missing Hb measurements. We assumed that these measurements were missing at random and excluded observations from these patients in our primary analysis. Because patients with missing Hb measurements had a lower median CD4+ count when compared with our analysis cohort, it is possible that our findings are biased. In our secondary analysis, we replaced missing observations using multiple imputations. We were encouraged to find that the 2 results were similar, suggesting our primary analysis was robust despite the missing data. Second, our cohort comprised individuals who were living and receiving care in an urban African setting, where resources for healthcare are often limited. As a result, there may be concerns about external validity, particularly because the causes of anemia may vary greatly across different settings. Finally, in the absence of consistent standards for defining anemia in this population within the literature, we used established toxicity levels developed by the US National Institute of Health Division of AIDS. We recognize that other guidelines have higher thresholds for anemia (<12 g/dL for females and <13 g/dL for males)18; however, in our setting, clinical action is typically not taken unless a Hb concentration is less than 10 g/dL. We believe that our definition of anemia has utility for clinicians practicing in similar environments.
In summary, Hb response early in the course of ART was associated with higher subsequent mortality in this programmatic cohort. Our findings emphasize the importance of continued Hb monitoring after ART initiation, even for those on non–ZDV-based regimens. It is unclear whether treatment of anemia early in the course of ART may lead to improved clinical outcomes; however, such an approach appears reasonable and would clearly have some health benefit. Further work is needed to better understand the mechanisms behind anemia-associated mortality among ART patients. Resource-appropriate interventions should be designed and evaluated with the goal of improving public health outcomes.
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anemia; hemoglobin; HIV; antiretroviral therapy; Africa; Zambia
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