Treatment of hepatitis C virus (HCV) infection is aimed at achieving a sustained virologic response (SVR), defined as undetectable HCV RNA using a sensitive polymerase chain reaction (PCR) assay 24 weeks after the end of treatment. Available evidence suggests that SVR is associated with reductions in long-term HCV-related morbidity and mortality in both HCV-monoinfected1,2 and HIV/HCV-coinfected patients.3
SVR rates with the current standard of therapy-pegylated interferon plus ribavirin-remain unsatisfactory: approximately 55% in HCV-monoinfected patients4-8 and 33% in HIV/HCV-coinfected patients.9
The most important baseline predictors of SVR in both monoinfected and coinfected patients are virus-related factors, namely, HCV genotype and HCV RNA.10,11 Response to treatment can also be affected by demographic factors (age, gender, weight, and race), histologic parameters (stage of fibrosis and steatosis), and treatment-related factors (dosing of ribavirin).4,5,11-13
Once treatment has been initiated, adherence and the fall in HCV RNA are important predictors of SVR. In particular, a rapid virologic response (RVR), defined as undetectable HCV RNA at week 4 of therapy, has been recognized as one of the most powerful predictors of SVR in both monoinfected14-16 and coinfected patients.17-19
In recent studies, the presence of insulin resistance (IR) has been associated with a reduced SVR in HCV-monoinfected patients treated with interferon plus ribavirin.20,21 The aim of the present study was to evaluate the association between IR and SVR in HIV/HCV-coinfected patients receiving the combination.
PATIENTS AND METHODS
The study population comprised patients from the HIV outpatient clinic of the “Gregorio Marañón” Hospital in Madrid, Spain. We carried out a retrospective review of the clinical records of HIV/HCV-coinfected patients who received interferon and ribavirin at our institution between July 2000 and March 2007. The eligibility criteria for anti-HCV therapy in our institution included absence of prior hepatic decompensation, CD4+ T-cell count >200 cells per microliter, stable antiretroviral therapy or no need for antiretroviral therapy, absence of active opportunistic infections, and no active drug addiction. Patients were counseled against the use of alcohol. For the purpose of this study, we excluded patients with diabetes mellitus according to the American Diabetes Association22 and those who had previously received interferon or ribavirin.
Clinical and Laboratory Assessment
The following information was obtained from the medical record: age, gender, risk category, Centers for Diseases Control and Prevention clinical category, prior and current antiretroviral therapy, and nadir CD4+ T-cell count. Height and weight were determined at baseline, and body mass index (BMI) was calculated as the weight in kilograms divided by the square of the height in meters. Patients were asked about their alcohol intake. We considered the consumption of more than 50 g of alcohol per day for at least 12 months as a high intake. Nadir CD4+ T-cell counts were defined as the lowest measured CD4+ T-cell count.
After an overnight fast and before the initiation of interferon and ribavirin, a blood sample was taken for a complete blood count, liver panel, basic metabolic panel, and coagulation tests. Simultaneously, a serum sample was immediately stored and frozen at −70°C for further assays. Apart from other routine analyses, CD4+ T-cell count and serum HCV and HIV RNA were measured at baseline and at weeks 12, 24, 36, and 48 during treatment and at weeks 12 and 24 after the end of treatment.
The degree of IR was estimated for each patient using the homeostatic model assessment (HOMA) method described by Matthews et al.23 An IR score (HOMA-IR) was obtained using the following formula: fasting plasma glucose (mmol/L) times fasting serum insulin (mU/L) divided by 22.5. This validated model has become a widely used clinical and epidemiological tool. IR was considered altered when the HOMA-IR score was 3.8 or higher based on a prevalence study carried out in a nondiabetic population in Spain24 and following previous works with HIV/HCV-coinfected patients,25,26 although there are no standard cutoffs clearly defined for IR. In this study, fasting glucose was determined on a fresh serum sample taken the day the patient initiated therapy with interferon plus ribavirin. Fasting insulin was measured in a frozen serum sample taken that same day. Insulin was measured using the Multiplex kit (LINCOplexTM; LINCO Research, St. Charles, MO). The Multiplex suspension bead array immunoassay was performed using the Luminex 100 analyzer (Luminex Corporation, Austin, TX) to identify the insulin level in frozen serum samples according to the manufacturer's specifications.
HIV infection was documented in all the patients by enzyme-linked immunosorbent assay and Western blot assay. All patients tested positive for specific HCV antibodies and had detectable serum HCV RNA assessed by PCR. The HCV viral load was measured by PCR (Cobas Amplicor HCV Monitor Test, Branchburg, NJ), and the results were reported in international units per milliliter. The HCV genotype was determined by hybridization of biotin-labeled PCR products to oligonucleotide probes bound to nitrocellulose membrane strips (INNO-LiPA HCV II; Innogenetics, Ghent, Belgium).
Before starting anti-HCV treatment, 116 of the 134 patients included in the on-treatment (OT) analysis underwent a liver biopsy on an outpatient basis following the recommendations of the Patient Care Committee of the American Gastroenterological Association.27 Ultrasound was routinely used to determine the percutaneous biopsy site. All patients gave their written informed consent.
Formalin-fixed paraffin-embedded liver tissue sections were stained by hematoxylin-eosin, Mason trichrome, and Perls iron and were evaluated by a pathologist who had no knowledge of the patient's clinical and laboratory data. Grading and staging of the liver biopsy followed the criteria of the METAVIR Cooperative Study Group.28 Liver steatosis was graded according to the percentage of hepatocytes containing visible macrovesicular fat droplets. Activity was graded as follows: A0 (no histological activity), A1 (mild activity), A2 (moderate activity), and A3 (severe activity).
Treatment Schedules and Outcomes
Patients were treated for 48 weeks with the combination of interferon plus ribavirin. Three types of interferon were used: standard non-pegylated interferon alfa-2b (Intron-A, Schering-Plough, Alcobendas, Spain) at a dose of 3 MU 3 times per week, pegylated interferon alfa-2a (Pegasys, Roche Farma S.A., Madrid, Spain) at a dose of 180 μg per week, or pegylated interferon alfa-2b (Peg-Intron; Schering-Plough) at a dose of 1.5 μg/kg per week. All patients received ribavirin (Rebetol; Schering-Plough) at a dose of 800 to 1200 mg per day according to body weight. An SVR was defined as an undetectable serum HCV RNA level (<50 IU/mL) 24 weeks after the end of treatment.29 A virologic failure was defined as the inability to achieve undetectable HCV RNA or a 2 log10 decrease in HCV RNA from baseline at week 12 after initiation of therapy, failure to achieve an undetectable serum HCV RNA level at week 24 of therapy, or an HCV viral rebound during therapy in patients with prior undetectable viremia.
We excluded patients who prematurely interrupted HCV treatment due to adverse events, patients who abandoned the study, or patients who were lost to follow-up. Comparisons between groups were made using the Mann-Whitney test or the t test for continuous variables and the χ2 test or Fisher exact test for categorical variables. For the OT analysis, we included patients who completed therapy or had a virologic failure. Multivariate logistic regression analysis was used to evaluate which factors were associated with the achievement of SVR. All tests were 2 tailed, and P values <0.05 were considered significant. The statistical analysis was performed using SPSS 15.0 software (SPSS Inc, Chicago, IL).
Baseline Characteristics of the Patients
During the study period, 218 HIV/HCV-coinfected patients from our institution were treated for HCV infection with interferon and ribavirin. HOMA-IR values at baseline were available for 162 patients of whom 28 (17%) prematurely interrupted HCV treatment due to adverse events, abandonment, or loss to follow-up. The OT analysis involved 134 patients whose baseline characteristics are shown in Table 1. The only significant difference between patients in the OT population and patients who interrupted therapy prematurely-according to characteristics listed in Table 1-was a higher frequency of liver steatosis in the former than in the latter; 68 of 134 (67%) vs. 8 of 28 (42%); P = 0.007. HCV genotype was available in 127 of the 134 patients included in the OT analysis. When we categorized patients according to their genotype, the proportion of patients with liver steatosis was significantly higher among those with genotype 2/3 29 of 34 (85%) than among those with genotype 1/4 38 of 65 (58%); P = 0.007. Twenty-five (19%) patients received standard interferon, and 109 (81%) received either pegylated interferon alfa-2a or alfa-2b. The mean dose of ribavirin was 14.9 mg·kg−1·d−1. The prevalence of IR calculated by the HOMA-IR index was 31%.
HOMA-IR values at baseline were significantly higher among patients with no SVR [median (interquartile ratio), 3.3 (1.9-5.5)] than among those with an SVR [1.9 (1.4-3.3)], P = .005. We also found a significant trend toward a lower SVR as HOMA-IR values at baseline increased (Fig. 1).
The SVR to interferon plus ribavirin by OT analysis in 134 patients, according to genotype and presence or absence of IR, is shown in Table 2. The frequency of SVR was significantly higher for patients with genotypes 2/3 than for those with genotypes 1/4 and significantly higher for patients without IR than for patients with IR. In patients infected by HCV genotypes 2/3, the frequency of SVR was significantly lower for patients with IR than for patients without IR [odds ratio (OR), 0.08; 95% confidence interval (CI): 0.01-0.48; P = 0.005). In patients infected by HCV genotypes 1/4, there was a trend toward a lower frequency of SVR for those with IR than for those without IR (OR, 0.4; 95% CI: 0.16-1.26; P = 0.13).
Three factors were independently and significantly associated with achieving an SVR: genotype 2/3 (OR, 6.7; 95% CI: 2.71-16.98; P < 0.001), absence of IR (OR, 3.3; 95% CI: 1.36-8.26; P = 0.008), and nadir CD4+ T-cell count (OR, 1.002; 95% CI: 1.00-1.00; P = 0.047). In a second model, age, gender, BMI, HCV RNA load, treatment with pegylated interferon, use of HIV protease inhibitors, presence of liver steatosis, and presence of advanced liver fibrosis (F3, F4) were included in the analysis. After adjusting for these variables, the same factors were identified as predictors of SVR (data not shown).
When we adjusted for genotype, HCV RNA load, presence of advanced liver fibrosis, and treatment with pegylated interferon, we found that the absence of IR at baseline was significantly associated with the probability of virologic response at weeks 4, 12, 24, 48, and 72 of treatment (Fig. 2).
Since the first report of the association between HCV infection and diabetes,30 the evidence connecting these 2 conditions has grown, and some authors have found that IR is a common feature in patients with chronic hepatitis C.31 In HCV-monoinfected patients, IR has been associated with fibrosis progression independently of obesity and liver steatosis.32,33 Interestingly, hyperinsulinemia and hyperglycemia can stimulate hepatic stellate cell mitogenesis and collagen synthesis.34,35
Several studies have reported a negative impact of IR on treatment outcomes in patients with chronic hepatitis C. In a study of 159 patients, Romero et al20 found that IR, fibrosis, and genotype were independent predictors of the response to antiviral therapy in HCV-monoinfected patients treated with pegylated interferon plus ribavirin. In another study carried out in 82 HCV-monoinfected obese patients with genotypes 2/3, those who attained SVR had lower mean serum insulin levels, fibrosis stage, and IR measured by HOMA-IR. After adjusting for fibrosis stage, patients with an HOMA-IR of less than 2 were 6.5 times more likely to achieve SVR than those with an HOMA-IR of 2 or greater.21
Little is known about the prevalence and associated factors of IR in HIV/HCV-coinfected patients. One cross-sectional study of 79 patients coinfected with HIV and HCV who underwent a liver biopsy showed that the prevalence of IR was 29.1%.25 The authors did not find an association between IR and liver fibrosis assessed by biopsy. In a cross-sectional study carried out in 201 HIV/HCV-coinfected patients who underwent liver biopsy to assess their suitability for anti-HCV therapy, we showed the prevalence of IR measured by HOMA to be 27%.26 In that study, we found that IR was independently associated with advanced liver fibrosis and a high BMI.
Few studies have assessed the correlation between IR and treatment response in HIV/HCV-coinfected patients treated with interferon and ribavirin. A study of 29 HIV/HCV-coinfected patients who started pegylated interferon alfa-2a plus ribavirin showed that patients without IR at baseline were more likely to reach an RVR and an early virologic response than others.36 In another study, it was found that genotype, HCV RNA, and IR were independent predictors of RVR.37 Merchante et al38 recently reported results on the relationship between IR and SVR in 155 patients from a multicenter cohort of HIV/HCV-coinfected patients who underwent therapy with pegylated interferon plus ribavirin. In this study, 55 patients (36%) achieved an SVR: 42 patients (38%) with an HOMA-IR <4 reached SVR vs. 13 (29%) of those with an HOMA-IR ≥4 (P = 0.27). Analyses restricted to patients infected by genotypes 1 or 4 showed similar rates of SVR among patients with an HOMA-IR below and above 4. In the multivariate analysis, genotype 3, a baseline HCV viral load below 600,000 IU/mL, and baseline low-density lipoprotein cholesterol were independently associated with SVR. The authors concluded that IR is not a relevant predictor of SVR to interferon plus ribavirin in HIV/HCV-coinfected patients.38
The results of our study contrast sharply with those reported by Merchante et al. We found a significant trend toward a lower SVR as baseline HOMA-IR values increased and significantly higher baseline HOMA-IR values in patients with no SVR than in those with SVR. We observed that IR at baseline was associated not only with an impaired virologic response at early stages of therapy (RVR, early virologic response) and end of treatment response but also with a reduced frequency of SVR. When we analyzed separately the association of IR with response categorized by genotype, we found that, among patients infected with HCV genotypes 2/3, the frequency of SVR was significantly lower in those with IR than in those without IR. In patients infected by HCV genotypes 1/4, there was a trend toward a lower frequency of SVR for those with IR than for those without IR, although this did not reach statistical significance. Of note, we found that IR, genotype, and nadir CD4+ T-cell count were independently associated with SVR by logistic regression analysis after adjustment for baseline variables, including BMI, protease inhibitors, and advanced liver fibrosis.
There were some differences between our study and that of Merchante et al. Our study was carried out in a single institution, whereas Merchante et al included patients from 4 centers. Second, the efficacy analysis in the study by Merchante et al was carried out using an intention-to-treat approach, considering all missing values as failures, whereas our efficacy analysis was performed on an OT basis, excluding patients who interrupted HCV treatment due to adverse events, abandonment, or loss to follow-up, to better assess the relationship between IR and virologic response.
In conclusion, our findings suggest that IR is an important determinant of poor response to anti-HCV therapy in HIV/HCV-coinfected patients. HOMA-IR should be included in the routine baseline evaluation of HIV/HCV-coinfected patients who are candidates for treatment with interferon and ribavirin.
The authors thank Thomas O'Boyle for writing assistance during the preparation of the article.
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