Interruption and Discontinuation of Highly Active Antiretroviral Therapy in the Multicenter AIDS Cohort Study

Li, Xiuhong MS*; Margolick, Joseph B MD, PhD†; Conover, Craig S MD, MPH‡; Badri, Sheila MD‡; Riddler, Sharon A MD§; Witt, Mallory D MD∥; Jacobson, Lisa P PhD*

JAIDS Journal of Acquired Immune Deficiency Syndromes:
Epidemiology and Social Science

Objective: Identify the determinants and consequences of interrupting and discontinuing highly active antiretroviral therapy (HAART) among a population-based cohort of HIV-infected men.

Methods: Longitudinal analyses were applied to 2916 person-visit pairs (589 men) of continuous HAART use, 243 person-visit pairs (154 men) during which HAART was interrupted, and 151 person-visit pairs (130 men) in which HAART was discontinued by the second visit. HIV RNA increase was defined as ≥1 log10 copies/mL across the visit pairs.

Results: Younger age, black race, geographic location, higher HIV RNA level, depression, shorter time on HAART, lower medication adherence, and not taking a lamivudine-containing regimen predicted interrupting HAART use. Younger age, higher HIV RNA level, depression, and taking an abacavir- or lopinavir-containing regimen predicted discontinuing HAART. Among men with ≤1000 HIV RNA copies/mL, approximately 5% of those who interrupted HAART for ≤7 days and those who continued HAART had an HIV RNA increase. Men with longer interruptions and HAART discontinuers had significantly higher rates of HIV RNA increases (35.7% and 70.5%, respectively). Discontinuation and long interruptions resulted in lower CD4 cell counts.

Conclusions: Host characteristics play a role in short interruptions, whereas longer interruptions may be clinically indicated. These longer stoppages had further virologic and immunologic consequences, however.

Author Information

From the *Department of Epidemiology and †Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; ‡Cook County Bureau Health Service, Infectious Diseases, John Stroger Hospital, Chicago, Illinois; §Department of Medicine, Division of Infectious Diseases, University of Pittsburgh, Pittsburgh, Pennsylvania; and ∥Division of HIV Medicine, University of California at Los Angeles School of Medicine, Los Angeles, California.

Received for publication November 25, 2003; accepted July 7, 2004.

The Multicenter AIDS Cohort Study is funded by the National Institute of Allergy and Infectious Disease, with additional supplemental funding from the National Cancer Institute (U01-AI-35042, 5-M01-RR-00722 [General Clinical Research Center], U01-AI-35043, U01-AI-37984, U01-AI-35039, U01-AI-35040, U01-AI-37613, and U01-AI-35041).

Reprints: Lisa P. Jacobson, Room E7646, Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, 21205 (e-mail:

Article Outline

Since its introduction in 1996, highly active antiretroviral therapy (HAART) has been shown to suppress virus replication and reduce morbidity and mortality among HIV-infected patients.1-5 Viral resistance, drug-related toxicity, and financial burden may lead clinicians and patients to interrupt therapy, however. Individuals may also experience drug holidays, defined as short unplanned temporary interruptions of all medications. These types of interruptions may be in accordance with the physician's recommendations and driven by practical reasons. For example, if a patient misses a prescription for antiretroviral therapy, the physician may prefer to halt all medications rather than use a partial suboptimal regimen. In addition, given medication-associated toxicities, pill burden, or incomplete understanding of the need for adherence to HAART, patients may miss their medications or self-discontinue treatment. The study of short-term interruption for ≤7 days has not been reported from settings outside clinical trials.

Given the substantial interest in this area, our goal was to determine the extent, determinants, and consequences of short-term interruption and prolonged discontinuation of HAART that occur in the population. We hypothesized that the proportion of the population discontinuing HAART has changed over time and is associated with markers of disease stage. We further hypothesized that short and limited discontinuation with resumption of HAART would not affect CD4 cell count. Current guidelines suggest a conservative approach to treatment; thus, clinicians are starting to recommend discontinuing HAART among those with relatively high CD4 cell counts and low HIV RNA levels. The consequences of such discontinuation are not known, however. Structured treatment interruption (STI) strategies are being tested in clinical trials6-10 but have not yet yielded sufficient data for translation into clinical practice. Using historical information in a cohort of HAART users may provide insight.

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Population and Study Design

The Multicenter AIDS Cohort Study (MACS) is an ongoing prospective study of HIV infection among homosexual men in the United States.11-14 A total of 5622 men were recruited: 4954 in 1984 through 1985 and 668 in 1987 through 1991 at 4 centers located in Baltimore, Chicago, Los Angeles, and Pittsburgh. The study questionnaires are available at The MACS study protocols were approved by institutional review boards of each of the participating centers, and informed consent was obtained from all participants.

Participants returned every 6 months for a detailed interview, a physical examination, quality-of-life assessment, and collection of blood for concomitant laboratory testing and storage. Positive enzyme-linked immunosorbent assays (ELISAs) with confirmatory Western blot tests were used to determine HIV seropositivity. HIV RNA levels were determined using the Roche Ultrasensitive RNA PCR assay (Hoffman-LaRoche, Nutley, NJ), with a detection limit of 50 copies/mL. T-lymphocyte subset levels were quantified by each MACS center using standardized flow cytometry.15,16

Self-reported use of antiretroviral medications at each visit was summarized to define whether participants were using HAART. HAART was defined according to the Department of Health and Human Services (DHHS)/Kaiser Panel17 guidelines as: (1) 2 or more nucleoside reverse transcriptase inhibitors (NRTIs: lamivudine [3TC], abacavir, zidovudine [ZDV], Combivir [ZDV + 3TC], stavudine [d4T], zalcitabine [ddC], didanosine [ddI], tenofovir, and Trizivir [ZDV + 3TC + abacavir]) in combination with at least 1 protease inhibitor (PI: amprenavir, indinavir, nelfinavir, ritonavir, saquinavir, and Kaletra [lopinavir]) and/or 1 nonnucleoside reverse transcriptase inhibitor (NNRTI: delavirdine, efavirenz, and nevirapine), (2) 1 NRTI in combination with at least 1 PI and at least 1 NNRTI, (3) a regimen containing ritonavir and saquinavir in combination with 1 NRTI and no NNRTIs, and (4) an abacavir- or tenofovir-containing regimen of 3 or more NRTIs in the absence of PIs and NNRTIs. Combinations of ZDV and d4T with either a PI or NNRTI were not considered HAART. The date of HAART initiation was defined as the midpoint between the last visit without report of HAART use and the first visit at which HAART use was reported.

Ascertainment of whether a participant interrupted all antiretroviral therapy at any time between visits was initiated as of April 1997. Beginning in April 1999, at each visit, we further collected information on the number of days off all an-tiretroviral therapies from the most recent time the participant stopped and thus were able to categorize HAART interruption as ≤7 or >7 days. It has been reported that rebound of HIV RNA to detectable levels during the first 7 days after cessation of HAART is uncommon.8,18 From April 2000 onward, we also elicited whether the participant' s physician prescribed or agreed to the interruption.

A nested cohort study was used to examine the extent, determinants, and consequences of discontinuation of HAART from April 1997 through March 2002. We used visit pairs (Vi, Vi+1) as the study unit, where HAART was reported at Vi and Vi+1 was the visit 6 months after Vi. We categorized participants into 3 groups: (1) continuing HAART-individuals who used HAART at both Vi and Vi+1, without stopping their medications for 2 or more consecutive days between Vi and Vi+1; (2) interrupted HAART-individuals who used HAART at both Vi and Vi+1 but reported not using any antiretrovirals for ≥2 consecutive days at least once between Vi and Vi+1; and (3) discontinued HAART-individuals who used HAART at Vi, stopped using all antiretrovirals between Vi and Vi+1, and were still off HAART at Vi+1. Participants could contribute multiple visit pairs within and across groups. When individuals reported stopping a specific medication, the reasons for such discontinuation were elicited.

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Statistical Analysis

Separate logistic regression models were used to identify determinants of interrupting HAART and discontinuing HAART, with continuing HAART use as the reference. Host characteristics, including age, race, depression (Center for Epidemiologic Studies Depression Scale [CES-D Scale] score of ≥16), recreational drug use, and markers of HIV disease stage (CD4 cell count, HIV RNA level, and clinical diagnosis of AIDS) as well as HAART use characteristics (antiretroviral therapy experience before HAART initiation, year of HAART initiation, number of years on HAART, number of drugs in HAART regimen, PI-containing regimen, and specific antiret-roviral drug) and calendar time at Vi were assessed as determinants of interrupting or discontinuing HAART in the following 6 months. The SAS GENMOD procedure (SAS Institute, Cary, NC) with a generalized estimating equation (GEE) was used to control for the within-subject correlation encountered in the longitudinal data. Predictors with probability values less than 0.10 in univariate models were examined in multivariate regression models. When assessing the role of adherence, we used data collected from April 1998, when information regarding adherence19 was ascertained. Men were defined as either 100% adherent or <100% adherent.19 Similarly, because the length of interruptions was not asked until April 1999, we restricted the analysis of interrupting HAART, stratified by length of time off HAART (≤7 or >7 days), to the data collected after that time.

To study the consequences of stopping HAART, we defined 2 outcomes based on changes of HIV RNA level and CD4 cell count from Vi to Vi+1. The first outcome, an increase of ≥1 log10 in HIV RNA from Vi to Vi+1, was assessed using logistic regression (with GEE), with HAART use as the independent covariate. The second outcome was the percent increase in CD4 cell count, defined as [(CD4i+1 - CD4i)/CD4i] × 100, and it was assessed using linear regression with GEE. Increases in CD4 cell count percentage >100% were set to 100% to reduce the effect of outliers on the mean. Because effects may differ by HIV RNA level, all analyses on the consequences of interruption and discontinuation of HAART were stratified according to HIV RNA level at Vi: (1) ≤1000 copies/mL, (2) 1001 to 10,000 copies/mL, and (3) >10,000 copies/mL.

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A total of 687 MACS participants initiated HAART from April 1997 to September 2001 and contributed 3950 person-visit pairs. Our analysis used 3310 person-visit pairs, including 2916 (589 men) in which men continued HAART throughout, 243 person-visit pairs during which an interruption was reported (154 men: 103 contributed 1 such visit pair, 30 had 2, and 21 had at least 3), and 151 visit pairs at which HAART was discontinued (130 men: 110 had discontinued once, 19 had 2 such visit pairs, and 1 had 3) We excluded 640 person-visits: 420 (10.6%) missed Vi+1, 123 (3.1%) changed to mono/combination antiretrovirals after Vi, and 97 (2.5%) had missing information. The majority (64%) of those who missed Vi+1 returned for later visits, and the percentages discontinuing and interrupting HAART were similar to those included in the analysis.

The percentage continuing HAART remained stable and ranged from 85.8% to 90.3% over time. The percentage interrupting HAART decreased from 10.5% in 1997 to 5.2% in 1999 and then increased to 7.7% in 2001 (Fig. 1). This inflection in the proportion interrupting HAART over time was significant (P = 0.013 for the quadratic term). The percentage discontinuing HAART increased from 2.9% in 1997 to 6.5% in 2001, with a significant linear trend (P = 0.016). The median time off HAART in those discontinuing HAART was 61 days (25th percentile: 33 days, 75th percentile: 110 days). Characteristics of the 3 different groups at Vi are presented in Table 1.

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Determinants of Interruption and Discontinuation of HAART

There were 2397 person-visit pairs (514 men) in the continuing HAART group, 197 person-visit pairs (127 men) in the interrupted HAART group, and 109 person-visit pairs (100 men) in the discontinued HAART group who had complete data on all potential predictors at Vi (Table 2). Univariately, younger age (P = 0.001), black race (P < 0.001), lower CD4 cell count (P = 0.011), higher HIV RNA level (P < 0.001), CES-D score ≥16 (P < 0.001), shorter time on HAART (P = 0.004), and not taking 3TC (P = 0.004) predicted interrupting HAART. Interruption differed by geographic location as well; those in Baltimore and Chicago were slightly more at risk for interrupting HAART than those in Pittsburgh and Los Angeles. Site did not modify the effects of other covariates of interruption (data not shown). With the exception of CD4 cell count, these factors remained independent predictors of interrupting HAART (see Table 2). After 1998, when adherence data were ascertained, men with lower adherence (<100%) at Vi were more likely to interrupt HAART in the following 6 months (odds ratio [OR] = 3.52, 95% confidence interval (CI): 2.18, 5.68; from the multivariate model). When adherence was included in the model, younger age and shorter time on HAART were no longer statistically significant, because younger age was associated with nonadherence (P = 0.004) and the restriction to after 1998 removed those with shorter times on HAART.

Among those interrupting HAART from April 1999 onward, 44.7% stopped all antiretrovirals for <4 days the last time, 25.0% stopped for 4 to 7 days, and 30.3% stopped for >7 days. Compared with continuing HAART, the independent predictors for interrupting HAART for ≤7 days (92 person-visit pairs) were younger age (OR = 1.30, 95% CI: 1.02, 1.65), black race (OR = 2.42, 95% CI: 1.23, 4.74), CES-D score ≥16 (OR = 2.17, 95% CI: 1.26, 3.73), and lower adherence to HAART (OR = 4.53, 95% CI: 2.66, 7.72). Those whose HAART regimen contained 3TC were less likely to interrupt therapy for ≤7 days (OR = 0.44, 95% CI: 0.25, 0.77). Predictors of missing all antiretrovirals for >7 days (40 person-visit pairs) were lower CD4 cell count (OR = 1.72, 95% CI: 1.08, 2.72), higher HIV RNA level (OR = 1.64, 95% CI: 1.22, 2.21), and CES-D score ≥16 (OR = 2.27, 95% CI: 1.03, 4.98)

Information on physician concordance for interruptions was collected since April 2000. Overall, 32.6% of the group who interrupted HAART reported that the interruption was prescribed by their physician. The extent of physician concordance differed by the length of the interruption: 20.3% of interruptions for ≤7 days were prescribed by physicians compared with 58.6% of interruptions for >7 days (P < 0.001).

As shown in Table 2, the factors univariately associated with discontinuing HAART were younger age (P = 0.003); lower CD4 cell count (P = 0.026); higher HIV RNA level (P < 0.001); CES-D score ≥16 (P < 0.001); and use of a regimen containing abacavir (P = 0.017), amprenavir (P = 0.018), or lopinavir (P = 0.005). Multivariately, CD4 cell count and using a regimen containing amprenavir did not independently predict discontinuing HAART. Restricting the analysis to data collected after 1998, <100% adherence predicted discontinuing HAART univariately (OR = 2.02, 95% CI: 1.20, 3.39). After controlling for other determinants, the effect of lower adherence was slightly diminished and was not statistically significant (OR = 1.62, 95% CI: 0.97, 2.71).

We also examined the self-reported reasons given by interrupters and discontinuers for discontinuing specific antiretrovirals. HAART discontinuers were significantly more likely to report stopping because of side effects than HAART interrupters: 58% versus 34%, respectively (P < 0.001). Also, 50.5% of the discontinuers reported that stopping was a result of their physician's recommendation compared with 32.6% of interrupters (P < 0.001). The proportion of discontinuers reporting discontinuation of HAART as a personal decision was similar to that of interrupters (33% and 30%, respectively, P = 0.505), however.

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Consequences of Interruption and Discontinuation of HAART

Among individuals with ≤1000 HIV RNA copies/mL at Vi, 5.2% of the men who continued HAART use had a ≥1 log10 HIV RNA increase in the next 6 months. Such increases were more likely in those interrupting or discontinuing HAART than in those continuing HAART (Table 3). The increase in HIV RNA among those interrupting HAART was mostly driven by those who stopped antiretroviral therapy for >7 days (35.7% had a ≥1 log10 HIV RNA increase; OR = 10.07, P < 0.001 compared with continuing HAART). Only 5.4% of those interrupting HAART for <7 days had such HIV RNA increases.

Among those with 1001 to 10,000 HIV RNA copies/mL at Vi, less than 3% of those interrupting or continuing HAART had a ≥1 log10 HIV RNA increase. Only those who discontinued HAART were significantly (P < 0.001) more likely to have such an HIV RNA increase (see Table 3). Few HAART users with >10,000 HIV RNA copies/mL had a ≥1 log10 increase in HIV RNA at Vi+1.

The average percent increases in CD4 cell count over 6 months for the continuing HAART group were 7.9%, 5.3%, and 5.5% for those with HIV RNA levels ≤1000, 1001 to 10,000, and >10,000 copies/mL at Vi, respectively. Average percent increases in CD4 cell count for those interrupting HAART overall did not significantly differ from those for the HAART continuers (Table 4). The mean percent changes in CD4 cell count for those interrupting HAART for ≤7 days were 13.7% (P = 0.152 compared with continuing HAART), 4.3% (P = 0.893), and −7.4% (P = 0.106) in the 3 HIV RNA strata, respectively. Those who interrupted HAART for >7 days also had a similar mean percentage of CD4 changes compared with the continuing HAART group when starting with ≤1000 HIV RNA copies/mL (13.3%; P = 0.552) and 1001 to 10,000 HIV RNA copies/ml (4.2%; P = 0.897). The mean percent change in CD4 for those who interrupted HAART for >7 days was −11.5% (P = 0.01) for those who had an HIV RNA level >10,000 copies/mL at Vi, however. Those who discontinued HAART also had changes in CD4 cell count of −13.2% (P < 0.001), −5.3% (P = 0.10), and −11.7% (P = 0.028) in the 3 HIV RNA strata, respectively, representing significant differences from those who continued HAART (see Table 4). The consequences of interrupting and discontinuing HAART did not change when adjusted for age and race (data not shown).

To assess whether discontinuation had longer consequences, we compared the 78% of the interrupters and the 42% of the discontinuers who resumed HAART from Vi+1 to Vi+2 and for whom we had biomarker data at Vi+2 with those who continuously used HAART. Although few of those who discontinued and resumed HAART had any subsequent increase in HIV RNA levels from Vi+1 to Vi+2 (data not shown), the discontinuers still were more likely to have a ≥1 log10 HIV RNA increase at Vi+2 as compared with that measured at Vi (compared with continuous HAART users; OR = 2.03, 95% CI: 0.72, 5.72). Similarly, although their percent change in CD4 cell count from Vi+1 to Vi+2 (ie, after resuming use of HAART) was similar to that of those who continuously used HAART, it did not compensate for the decrement observed from Vi to Vi+1. Whereas the continuous HAART users had an annual increase of 10.6% (95% CI: 9.2, 12.0) on average by Vi+2, the discontinuers overall had an annualized loss of 1.3% of their Vi CD4 cell count at Vi+2, representing a significant (P = 0.02) difference in the change of CD4 cell count. Compared with those who continuously used HAART, there were no significant differences in the change of HIV RNA level and CD4 cell count at Vi+2 for those who interrupted therapy between Vi and Vi+1.

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There has been great interest in the interruption and discontinuation of HAART in clinical practice because of drug resistance, severe toxicity, and the high cost of HAART. In this study, the proportion of HAART users interrupting therapy decreased since 1997 but increased after 1999. The low proportion discontinuing therapy has increased over time. The increasing trend may reflect changes in standard treatment guidelines, suggesting a more conservative approach, difficulty in maintaining continuous use of HAART, and/or the impact of alternative interruption strategies recently introduced in clinical trials6-9 as well as in the news. The increasing trend of discontinuation of HAART in this cohort was consistent with a report from the Women's Interagency HIV Study (WIHS).20

Recommended interruptions (ie, those made in concordance with physicians) also may have resulted from practical needs. Physicians may prefer that all medications are halted rather than using partial suboptimal regimens. Little is known about the consequences of interrupting HAART by the clinicians or patients outside of the STI clinical trials.6-10 Therefore, we studied not only the consequences but the determinants of HAART interruption to understand better why interruptions occur in the general HIV-1-infected population. Whereas our analysis of independently ascertained markers of HIV disease stage (low CD4 cell count and high HIV RNA level) predicted interrupting HAART for >7 days, host characteristics (eg, age, race, lower adherence) were associated with short interruption of HAART (≤7 days). These factors, which indicate personal decision making, were consistent with the finding that those with short interruptions were less likely to have their interruptions prescribed by their physicians, indicating that the short interruptions may be a compliance issue. The finding that taking a 3TC-containing regimen was protective against short-term interruption might be explained by the fact that 3TC has lower toxicity than other antiretroviral drugs.17

Future analyses need to differentiate those who discontinue HAART for personal reasons, side effects, and as a result of physician recommendation, because these causes relate to different lengths of time off HAART and may have different consequences.

A pilot study reported that HIV RNA was suppressed to low levels and CD4 cell count returned to preinterruption levels after resumption of HAART,7 consistent with our findings of no significant consequences of short-term HAART interruption (≤7 days) when compared with uninterrupted use of HAART. Similarly, although a greater proportion of those interrupting for >7 days among those with <1000 HIV RNA copies/mL had HIV RNA increases, the CD4 cell count remained stable. These data suggest that among individuals whose HIV RNA level is relatively low, HAART interruptions may not significantly affect immunologic outcomes at 6 months. We could not examine how long the person was back on HAART when the HIV RNA level and CD4 cell count were measured at Vi+1, but there was no effect on the HIV RNA level and CD4 cell count measured at Vi+2 at least 6 months after the interruption occurred. Results from other studies have been inconsistent. Taffe et al21 showed that occasional interruptions of 1 to 3 months did not worsen clinical disease outcome in 3 to 4 years when the HIV RNA level is low and the CD4 cell count is high, supporting the finding that with resumption of HAART, the occasional interruption may not be detrimental among these people. Yet, frequently reported short interruptions have been shown to lead to virologic failure.22 Data from clinical trials such as Swiss-Thai-Australia Treatment Interruption Trial (STACCATO),22 in which interruptions are driven by CD4 levels, should offer additional information on the effects of the longer interruptions that are anticipated in these individuals.

The observation that higher HIV RNA level and lower CD4 cell count predicted discontinuation of HAART is consistent with the findings of other studies.20,23-25 We also found that depression and lower adherence to HAART were associated with subsequent discontinuation of HAART. Depressive symptoms have been associated with reduced adherence to HAART.26,27 In addition, we found that younger age and taking a regimen containing abacavir or lopinavir predicted discontinuing HAART. Although these regimens may represent salvage therapy, use of antiretroviral therapy before HAART initiation, length of time on HAART, and number of prior HAART regimens were not independently associated with discontinuation.

The increase in HIV RNA level and decrease in CD4 cell count observed after a 6-month interval among HAART discontinuers were similar to results in other studies.6,7,20,28 Although these individuals demonstrated an increase in CD4 cell count on subsequent resumption of HAART, they still had a significant decrement at the next visit (at least 6 months after the discontinuation) compared with those who continuously used HAART. The observed detrimental effect on HIV markers from prolonged treatment discontinuation is consistent with the poor prognosis associated with nonadherence.29-33 Because discontinuers are more likely to have a history of lower adherence, they may be primed for a worse prognosis than those who continue HAART. Although we stratified by HIV RNA level at Vi, thus accounting, in part, for the effect of a history of lower adherence, there still may be some residual effect (ie, lower adherers may have higher viral loads within the strata).

Although these data were from a large cohort study, there are limitations. Our cohort does not include women and children, and most of the men have been infected for many years and had experience with antiretroviral therapy when starting HAART; thus, our findings might not be generalizable to all HIV-infected persons. Also, the numbers of observations in subgroups defined by missing all antiretrovirals for ≤7 days or >7 days and an HIV RNA level >1000 copies/mL at Vi are relatively small; therefore, inferences should be drawn with caution. In addition, the information on medication use, including adherence, is based on self-report; thus, the proportions interrupting HAART may be underestimates. These data were collected independent of health care setting (ie, not by the primary care physician or in a clinical trial setting), however, and thus should minimize the overreporting of continuous HAART use one may expect from patients. Another advantage is that the characteristics assessed as predictors were determined before the outcome.

In summary, our findings indicate that interruption and discontinuation of HAART are gradually increasing in the population. Short-term HAART interruption (≤7 days) among chronically infected HIV patients with an HIV RNA level <10,000 copies/mL did not seem to affect the treatment benefit. Thus, it is possible that short interruptions may be associated with reductions in cost and drug-related toxicity, although these reductions are probably minimal. This potentially viable treatment strategy would need to be tested in large controlled trials. We also could not assess the effect of repeated interruptions; thus, the results need to be viewed with caution. Longer interruptions, as shown here and in a recently reported study,34 seem to have negative effects on HIV disease. In a recent presentation,35 longer interruptions were associated with the development of drug-resistant virus, thus limiting the choice of antiretrovirals on resumption of HAART. Long-term effects of short- and long-term interruptions need to be studied, not only on immune reconstitution but on viral drug resistance and viral replicative capacity. Among those with more advanced HIV disease, patient education, particularly among younger individuals, is needed to emphasize the importance of minimizing unnecessary treatment interruptions. Given the relation to depression, offering mental health services may enhance continuous use of HAART.

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The MACS includes the following institutions and individuals: The Johns Hopkins University Bloomberg School of Public Health (Baltimore): Joseph B. Margolick (Principal Investigator), Haroutune Armenian, Barbara Crain, Adrian Dobs, Homayoon Farzadegan, Shenghan Lai, and Justin McArthur; Howard Brown Health Center (Chicago), The Feinberg School of Medicine, Northwestern University (Chicago), and Cook County Bureau of Health Services (Chicago): John P. Phair (Principal Investigator), Joan S. Chmiel (Co-Principal Investigator), Sheila Badri, Bruce Cohen, Craig Conover, Maurice O'Gorman, Frank Pallela, Daina Variakojis, and Steven M. Wolinsky; University of California, University of California at Los Angeles Schools of Public Health and Medicine (Los Angeles): Roger Detels and Beth Jamieson (Principal Investigators), Barbara R. Visscher (Co-Principal Investigator), Anthony Butch, John Fahey, Otoniel Martínez-Maza, Eric N. Miller, John Oishi, Paul Satz, Elyse Singer, Harry Vinters, Otto Yang, and Stephen Young; University of Pittsburgh, Graduate School of Public Health (Pittsburgh): Charles R. Rinaldo (Principal Investigator), Lawrence Kingsley (Co-Principal Investigator), James T. Becker, Phalguni Gupta, John Mellors, Sharon Riddler, and Anthony Silvestre; Data Coordinating Center: The Johns Hopkins University Bloomberg School of Public Health (Baltimore): Lisa P. Jacobson (Principal Investigator), Alvaro Muñoz (Co-Principal Investigator), Haitao Chu, Stephen R. Cole, Stephen J. Gange, Janet Schollenberger, Eric Seaberg, Sol Su, and Xiuhong Li; National Institutes of Health, National Institute of Allergy and Infectious Diseases (Bethesda): Carolyn Williams and Robin Huebner; and National Institutes of Health, National Cancer Institute (Bethesda): Jodi Black. Web site located at

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HIV; highly active antiretroviral therapy; interruption; discontinuation; HIV RNA; CD4 cell count

© 2005 Lippincott Williams & Wilkins, Inc.