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MP 2.04.49

Laboratory Testing for HIV Tropism

Medical Policy    

Original Policy Date

Last Review Status/Date
Reviewed with literature search/3:2013
  Return to Medical Policy Index


Our medical policies are designed for informational purposes only and are not an authorization, or an explanation of benefits, or a contract.  Receipt of benefits is subject to satisfaction of all terms and conditions of the coverage.  Medical technology is constantly changing, and we reserve the right to review and update our policies periodically.


HIV tropism testing can determine the predominant co-receptor protein used by the human immunodeficiency virus (HIV) to infect target cells. Tropism testing can help select patients for treatment with HIV co-receptor antagonists, such as Maraviroc, which block specific co-receptor proteins.

The human immunodeficiency virus (HIV-1), which causes acquired immunodeficiency syndrome (AIDS), uses co-receptor proteins (either CCR5 or CXCR4) on the surface of target cells to enter and infect the cells. The most commonly transmitted strains of HIV-1 bind to CCR5 and are said to have “tropism” for CCR5-expressing cells. Dual or mixed (D/M) tropic viruses can bind to either receptor type. It is estimated that around 85% of treatment-naïve patients harbor CCR5-tropic virus only, around 15% harbor D/M virus, and less than 1% are infected with CXCR4-tropic virus alone. CXCR4-tropic virus is associated with immunosuppression and later stages of disease. New, experimental drugs, termed co-receptor antagonists, have been designed to interfere with the interaction between HIV-1 and its co-receptors.

Maraviroc (Selzentry™, Pfizer) is the first co-receptor antagonist to be approved by the U.S. Food and Drug Administration (FDA). Maraviroc is a selective, slowly reversible, small-molecule antagonist of the interaction between human cell surface CCR5 and HIV-1 gp120, also necessary for HIV-1 cell infection. Blocking this interaction prevents CCR5-tropic HIV-1 entry into cells. However, CXCR4-tropic HIV-1 entry is not prevented. According to the label, maraviroc, in combination with other antiretroviral agents, is indicated for adult patients who:

  • are treatment experienced, or
  • are treatment naïve (approved as of November 24, 2009);
  • are infected with only CCR5-tropic detectable HIV-1;
  • have evidence of viral replication.

The FDA-approved full prescribing information for the drug states that “Tropism testing must be conducted with a highly sensitive and specific tropism assay that has demonstrated the ability to identify patients appropriate for [maraviroc] use.” This is because efficacy was not demonstrated in a Phase II study of maraviroc in patients with D/M or CXCR4-tropic HIV-1. Due to potential adverse effects (hepatic and cardiotoxicity), maraviroc should only be used in indicated patients.

HIV tropism testing is available by either phenotypic or genotypic methods. Tropism testing with a phenotypic assay, a cellular-based assay that functionally determines tropism, is available with the enhanced sensitivity Trofile™ (Monogram Biosciences, South San Francisco, CA) assay (ESTA). This phenotypic assay uses virus stocks pseudotyped with envelope sequences derived from patient plasma to infect cell lines engineered to express CCR5 or CXCR4 HIV-2 co-receptors. Genotypic tropism testing is based on sequencing the third variable (V3) loop of the HIV glycoprotein 120 gene, because the V3 loop interacts with the HIV co-receptor, and mutations in V3 are associated with measurable changes in HIV tropism. Tropism assignment is derived from the sequence data using a bioinformatic algorithm such as geno2pheno. Genotypic tropism assays are available from commercial and other laboratory sources. For example, Quest Diagnostics Inc. offers the HIV-1 Coreceptor Tropism test.


HIV tropism testing with either the phenotypic assay or V3 population genotyping (see Policy Guidelines) may be considered medically necessary for selecting patients for treatment with HIV co-receptor antagonists such as maraviroc. Patients indicated for testing:

  • have evidence of viral replication, and
  • have failed multiple antiretroviral treatment regimens, or
  • are treatment naïve.

HIV V3 deep sequencing (synonyms: ultra-deep sequencing; pyrosequencing; next generation sequencing) for selecting patients for treatment with HIV co-receptor antagonists is considered investigational.

HIV tropism testing without immediate plans to prescribe HIV co-receptor antagonists such as maraviroc is not medically necessary.

Repeat HIV tropism testing during co-receptor antagonist treatment or after failure with co-receptor antagonists is investigational.

HIV tropism testing to predict disease progression (irrespective of co-receptor antagonist treatment) is investigational.

Policy Guidelines

There are no specific CPT codes for HIV tropism testing. In coding advice disseminated by NHIC, a local Medicare carrier, it was suggested that CPT code 87999 be used for this test along with “Trofile test for maraviroc” in the claim comments field.

Testing should be conducted immediately prior to intended prescribed use of maraviroc to obtain the most accurate prediction of tropism at the start of treatment.

Either phenotypic or V3 population genotypic testing may be used to determine HIV tropism; both are not necessary.

Benefit Application
BlueCard/National Account Issues

The FDA has not regulated the Trofile test because it is a laboratory-developed test (LDT) conducted only at Monogram Biosciences’ CLIA-licensed laboratory, and it does not meet the definition of an in vitro diagnostic multivariate index assay (IVDMIA), the only type of LDT that the FDA is currently regulating. Laboratories performing LDTs not regulated by the FDA must only be certified for high-complexity testing under the Clinical Laboratory Improvement Amendments of 1988.


This policy was created in 2007 and updated periodically with literature review. The most recent update with literature review covered the period of November 2009 through January 2013.

Literature Review

The approval by the U.S. Food and Drug Administration (FDA) of maraviroc is based on safety and effectiveness data from 3 studies in adult subjects infected with CCR5-tropic human Immunodeficiency virus (HIV-1): A4001027 and A4001028, in antiretroviral treatment-experienced adult patients and A4001026 in treatment-naïve patients.

Clinical studies in treatment-experienced patients

The Maraviroc versus Optimized Therapy in Viremic Antiretroviral Treatment-Experienced Patients (MOTIVATE) 1 and 2 trials assessed the efficacy of maraviroc in patients previously treated or resistant to 3 antiretroviral drug classes and with HIV-1 RNA levels exceeding 5,000 copies/mL. (1) MOTIVATE-1 was conducted in Canada and the United States, and MOTIVATE-2 in Australia, Europe, and the United States, using identical study designs. A total of 1,075 patients were randomized to 3 trial arms, and 1,049 received at least one dose of study drug: placebo (n=209), maraviroc once daily (n=414), or maraviroc twice daily (n=426). Selected subjects had only CCR5-tropic HIV-1 infections, as determined by the original Trofile assay for HIV tropism (see ‘Tropism Testing,’ following). At 48-weeks follow-up in an intention-to-treat analysis, 16% in the placebo group and 45% in both maraviroc-treated groups had HIV-1 RNA levels less than 50 copies/mL. The mean increase in CD-4 count from baseline was 60 in the placebo group compared to 120 in the maraviroc groups. Based on the early trial results and review by the FDA Antiviral Drugs Advisory Committee, the FDA concluded that, compared to placebo, maraviroc significantly reduced HIV RNA copy number, and significantly increased CD4 cells, both validated markers of improved health outcomes. (2) At nearly 2 years of follow-up (96 weeks), 81% to 87% of maraviroc-treated patients maintained these responses with no new or unexpected events impacting safety. (3)

In contrast, in a trial of 167 patients infected with dual- or mixed-tropic HIV-1, randomized to receive optimal therapy plus maraviroc or placebo, there was no difference in outcomes between treatment groups, indicating maraviroc treatment failure in patients harboring assay-detectable CXCR4-tropic HIV-1 populations. (4)

Clinical studies in treatment-naïve patients

The MERIT (Maraviroc versus Efavirenz in Treatment-Naive Patients) study is a randomized, double-blind, multicenter study in subjects infected with CCR5-tropic HIV-1 according to the original Trofile assay. Patients had plasma HIV-1 RNA levels of at least 2,000 copies/mL and did not have: 1) prior antiretroviral therapy for longer than 14 days, 2) an active or recent opportunistic infection or primary HIV-1 infection, or 3) resistance to zidovudine, lamivudine, or efavirenz. Subjects were randomized to 2 doses of either maraviroc or efavirenz, each in combination with zidovudine/lamivudine. In a pre-planned interim analysis, the lower dose of maraviroc failed to meet prespecified efficacy criteria and was discontinued. Patients were stratified by screening HIV-1 RNA levels and by geographic region. The median CD4 cell counts and mean HIV-1 RNA at baseline were similar for both treatment groups.

At 96 weeks, after re-analysis using results from an enhanced sensitivity Trofile assay (see ‘Tropism Testing,’ following), virologic response rates in both treatment arms were approximately equal, and there were fewer discontinuations due to adverse events in the maraviroc arm. (5)

Although most newly infected patients harbor CCR5-tropic HIV virus alone, a study of 150 individuals from 2 recent seroconverter cohorts documented 4% infection with detectable CXCR4-tropic virus (either mixed or, rarely, CXCR4-only), indicating that tropism analysis is necessary, even for the recently infected. (6)

Tropism testing

For the clinical studies of patients with treatment failure, tropism at enrollment and again at baseline was determined using the original phenotypic Trofile assay for 2,560 potential enrollees; 56% were CCR5-tropic only and were eligible for the clinical trials. Most other patients had dual/mixed HIV infection; CXCR4-infection alone is rare. Of the patients enrolled, 90% had CCR5-tropic virus at baseline, 4% had dual-mixed tropic virus, and 5% had non-typable virus infection.

Based on information presented to the FDA Antiviral Drugs Advisory Committee and on published assay validation data, (7) the original phenotypic Trofile assay had a turnaround time of 14 to 18 days, failed to work in 3–7% of patients, and required at least 1,000 copies/mL of HIV RNA. The assay was 100% effective in detecting model CXCR4-tropic or dual/mixed HIV present in a 10% mixture, and 83% effective at a 5% mixture. Validation studies also indicated 100% accuracy of results for 38 samples with known tropism, and 100% reproducibility including repeat assays using multiple operators, instrumentation, reagent lots, and conducted over a 14-day period. No false-positive results were obtained on samples that were HIV-negative but positive for either hepatitis B or C virus.

An enhanced sensitivity Trofile assay (ESTA) has replaced the original Trofile. The ESTA can detect CXCR4-tropic virus present at levels less than 0.3% of the total virus population, and at that level of virus or higher, the assay is stated to be 100% sensitive. (8) Total viral concentration of at least 1,000 copies/mL is required. However, ESTA remains limited by long turnaround time and the relatively high minimum level of viremia required, making it not useful in patients in virological failure with low viremia. Additionally, a small proportion of samples cannot be successfully phenotyped with either generation of the Trofile assay. (9)

The MERIT study of treatment-naïve patients was retrospectively reanalyzed using ESTA; approximately 15% of the subjects originally identified as CCR5-tropic had dual/mixed- or CXCR4-tropic virus by ESTA. Removing these from the analysis resulted, as already noted, in similar responses in both trial arms, indicating that maraviroc in a combination regimen is at least as good as another well-accepted combination regimen for treatment-naïve patients. (5)

Wilkin et al. used ESTA to re-analyze samples from 4 large cohort studies that had originally been evaluated for HIV tropism with the original Trofile assay. (10) Nine percent to 26% of patients with CCR5-tropic virus by the original Trofile assay had CXCR4-using virus by ESTA.

Tropism testing for treatment monitoring and at virologic failure

The prominent reason for individual treatment failure in the clinical studies was outgrowth of a minor CXCR4-tropic virus population not detected at screening. However, treatment failure with CCR5-tropic virus alone also occurred, indicating that resistance to CCR5 antagonists occurs independent of tropism. In vitro studies have provided extensive information on resistance; mechanisms may involve the ability of HIV to bind the CCR5 inhibitor-receptor complex. Resistance to CCR5 antagonists has been associated with increased affinity for CCR5, changes in the gp 120 V3 loop, and with other gp 120 (or other envelope) changes.

HIV-1 viral load is a strong prognostic indicator of HIV disease progression, and suppression of viral load is a critical goal of antiretroviral therapy. (9) Viral rebound (virologic failure) is typically followed by a reduction in CD4 cell count (immunologic failure), and if not adequately addressed by changes in treatment, by HIV-related events (clinical progression). Thus, success of any antiretroviral treatment regimen is monitored by measuring HIV-1 RNA level and CD4 cell count; significant changes direct patient management.

Viral strains transmitted in vivo are usually CCR5-tropic. (11) Over time and more often after antiretroviral treatment, detectable CXCR4-tropic virus emerges in about half of patients and is associated with rapid CD4 cell depletion and clinical disease progression. (12, 13) However, patients whose infection remains predominately CCR5-tropic can also experience disease progression. The significance of CXCR4-tropic virus emergence is unknown.

A concern regarding treatment with CCR5 co-receptor antagonists is that small, undetectable populations of CXCR4-tropic virus would be enriched and would accelerate disease progression. However, in a randomized, placebo-controlled Phase II study of maraviroc treatment of patients with dual or mixed (D/M)-tropic infections, there was no evidence that this was the case. (14) The association of CXCR4 tropism (defined with the original Trofile assay) with clinical progression has been shown to be independent of CD4 cell count and HIV-1 RNA level (adjusted hazard ratio: 3.82, 95% CI: 1.69–8.60, p=0.001 compared to patients with CCR5-tropic infection only). (15)

Fatkenheuer et al. performed a post-hoc analysis of the virologic response according to tropism at baseline and at treatment failure (16) using pooled data from the MOTIVATE 1 and 2 trials. Virologic failure occurred in 53% of placebo-treated patients and in 22-23% in the maraviroc treatment arms. However, of the 133 treatment failures in the maraviroc groups, 76 (57%) had CXCR4 or D/M tropism compared to only 6 of 95 (6%) in the placebo group, (16) raising concerns that maraviroc treatment could lead to emergence of CXCR4-tropic subpopulations and more rapid development of clinical progression. This was not the case, as the CXCR4 maraviroc treatment failures were not associated with declines in CD4 cell counts nor with disease progression.

There currently is no recommended management change based on a CCR5 to CXCR4 tropism switch during treatment with maraviroc. Treatment failure is detected by increased viral load and decreased CD4 cell count, (9) indicating that maraviroc treatment can be discontinued. The most common mechanism of maraviroc treatment failure is emergence of a CXCR4-tropic viral population. However, this is not necessarily correlated with rapid clinical progression. (17) Aside from the specific situation of maraviroc treatment failure, CXCR4-topic virus infection has been associated with more rapid disease progression, compared to CCR5 infection, in several studies (e.g. see Wilkin et al., (10)) but current management recommendations are based on monitoring CD4 cell count and viral load, rather than viral tropism.

V3 population genotyping to determine tropism

The Trofile assay is a cell-based, functional (phenotypic) assay. Genotypic assays are based on the sequencing of the patient-derived HIV-1 gp 120 V3 domain, which determines the protein amino acid sequence for the major determinant of co-receptor binding. This sequencing method results in a V3 sequence that represents the average or dominant viral population sequence for each patient. The HIV V3 sequence is used to infer HIV-1 tropism using web-based bioinformatic interpretation tools developed from prior data. These are most often geno2pheno co-receptor (G2P; available online at: ) (18) and position-specific scoring matrices (PSSM; available online at; ). (19) Genotyping can be conducted on either viral RNA samples (plasma) or on proviral DNA (peripheral blood mononuclear cells), the latter allowing tropism determination in the context of undetectable viremia. (20) Other potential advantages of genotypic assays are reduced cost, shorter turnaround time, fewer sample failures. (21)

Early genotyping studies with comparisons to original Trofile assay results reached contradictory conclusions regarding the adequacy of genotyping for predicting CXCR4 co-receptor usage. Some of the variability in genotype-phenotype assay correlation may have been due to the lower sensitivity of the original Trofile assay, and some variability may have accrued from inclusion of samples containing HIV subtypes other than B (the dominant form in Europe, the Americas, Japan, Thailand, and Australia). Ultimately, the best indication against which tropism assay results should be compared is the virological outcome of patients who receive CCR5-antagonist medication. (22)

Table 1 summarizes the results of studies comparing V3 genotyping results to virologic outcomes after maraviroc treatment. Because most studies use G2P for interpretation, only these results are presented. Where reported, results of original Trofile and enhanced-sensitivity Trofile assay results are also shown. Only the study reported by Gonzalez-Serna was prospective; for the others, V3 genotyping was conducted retrospectively on banked samples. McGovern (2010) likely includes data reported by Harrigan (2009). Results depend on the false-positive rate (FPR) cutoff value chosen for the G2P algorithm. If the result provided by G2P for a specific V3 sequence is higher than the chosen cut-off, the prediction of HIV-1 co-receptor tropism is CXCR4. Because the G2P distributions for CCR5- and CXCR4-tropic viruses overlap, no cutoff value allows perfect classification. Using a higher cutoff value is considered a conservative choice because predictions of CXCR4-tropism are more likely to be true predictions; the trade-off is that some true CXCR4-tropic HIV infections will be falsely identified as CCR5-tropic. For example, a cutoff value of 5.75% was optimized retrospectively for the MOTIVATE trial data, (23) but for routine clinical practice, the European guidelines on HIV-1 tropism testing recommend a cut-off of 10% for sequencing of samples in triplicate, or a cut-off of 20% when only a single sequence is generated. (24)

The data in Table 1 indicate that, depending on the G2P cutoff value chosen, V3 sequencing results can be generated that are very similar in their ability to predict response to maraviroc to both the original Trofile and the enhanced sensitivity Trofile assays. The Gonzalez-Serna study reports somewhat different results, with lower sensitivity and higher specificity for maraviroc response using similar G2P cutoff values. This study prospectively enrolled patients attending the infectious disease service of a university hospital, as opposed to the other retrospective studies of carefully selected clinical trial participants, but was also much smaller. Sequencing in this study was not done in triplicate as it was in the other studies.

Table 2 summarizes studies that evaluated the results of V3 sequencing using enhanced sensitivity Trofile assay (ESTA) as the reference standard; treatment outcomes were not considered in these analyses. All studies sequenced HIV V3 RNA from plasma (standard assay); 2 additionally sequenced HIV V3 DNA from whole blood, which targets proviral DNA (useful for patients with low plasma levels of virus). These studies are much smaller than the studies in Table 1, and largely, where it could be determined, did not test samples in triplicate. It is important to remember that the test performance characteristics reported in Table 2 cannot be compared to those reported in Table 1, as the reference standards differ. In general, the sensitivity results indicate that V3 genotyping detects somewhat fewer CXCR4-tropic viral samples than does ESTA; the specificity results indicate that the FPR is not high, i.e. few CCR5-tropic samples are identified as CXCR4-tropic. Assay concordance is relatively high. Where reported, genotyping results for proviral DNA appear very similar to those for RNA in paired samples from the same patient population.

Recently presented results of European cohort studies have shown maraviroc virologic extended response rates of 69-82% in those patients in which HIV variants were genotypically classified CCR5-tropic. (25)

Overall and based largely on the studies of tropism assays with reference to maraviroc treatment outcome (Table 1), the evidence suggests that HIV V3 genotyping classifies patients as well as Trofile assays. Genotyping has additional advantages of shorter turnaround time, ability to generate results for patients who cannot be assayed by Trofile, and more access to assay providers.

Table 1. Performance of HIV V3 genotyping, Trofile, and ESTA assays with reference to maraviroc treatment outcomes.





RT-PCR replicates

Virologic Response Definition

V3 Genotyping algorithm

V3 Genotyping vs virologic response to MVC

Original Trofile vx virologic response to MVC

ESTA vs virologic response to MVC

McGovern 2010 (Abs) (25)


Drug-naïve patients from MERIT trial


<50 copies/mL at week 48

G2P, FRP=5.75%




Harrigan 2009 (Abs) (26)


Treatment experienced patients from MOTIVATE and 1,029 studies


<50 copies/mL or reduction > 2 log at week 8

G2P, FPR=5%








Gonzalez-Serna 2011 (27) 


Patients with persistent viral load and on treatment hiatus 


<50 copies/mL or reduction > 1 log on day 8

G2P clonal,











Sens = 68%


Spec = 83%



McGovern 2010 (28)


Treatment-experienced patients from MOTIVATE and 1,029 studies


<50 copies/mL or reduction > 2 log at week 8 

G2P, FPR=5%








Abbreviations: RT-PCR, reverse-transcriptase polymerase chain reaction; ESTA, enhanced sensitivity Trofile assay; MVC, maraviroc; G2P, geno2pheno co-receptor system; FPR, false-positive rate (used as cutoff value); Sens, sensitivity; Spec, specificity; Conc, concordance; MERIT, (Maraviroc versus Efavirenz Regimens as Initial Therapy trial; MOTIVATE, Maraviroc Plus Optimized Therapy in Viremic Antiretroviral Treatment-Experienced Patients trials; NR, not reported

Table 2. Performance of HIV V3 genotyping with reference to enhanced sensitivity Trofile assay.




RT-PCR replicates

V3 Genotyping algorithm

V3 genotyping vs ESTA




Prosperi 2010 (21)


Patients failing antiretroviral treatment


G2P clonal, FPR=5.75% G2P clonal, FPR=10%


G2P clonal, FPR=5.75%


G2P clonal, FPR=10%

RNA: 55%


DNA: 68%










Svicher 2010 (20) 


63% treatment-experienced patients


G2P clonal, FPR=5%


G2P clonal, FPR=10%







Sanchez 2010 (29)


Naïve and treatment-experienced patients

1x (?)

G2P clonal, FPR=5%


G2P clonal, FPR=10% 







Strang 2009 (Abs) (30) 


Patients evaluated for maraviroc therapy




FPR 1-20% 




Pou 2009 (Abs) (31) 


Banked samples, pre-ART



RNA: 40%
DNA: 36%



Abbreviations: RT-PCR, reverse-transcriptase polymerase chain reaction; ESTA, enhanced sensitivity Trofile assay; G2P, geno2pheno co-receptor system; FPR, false-positive rate (used as cutoff value); Sens, sensitivity; Spec, specificity; Conc, concordance; NR, not reported

Tropism testing by deep sequencing

Because of concern that standard V3 sequencing methods used for tropism testing, might miss clinically significant minor HIV variants, so-called “deep sequencing,” i.e., V3 sequencing using next generation sequencing methods has been investigated for utility in tropism testing. While standard sequencing essentially determines a population average V3 loop sequence, deep sequencing allows simultaneous sequencing and quantifying of thousands of individual V3 variants within a viral population, From this, the proportion of non-R5 variants in a given sample can be calculated using interpretation tools similar to those for standard V3 genotyping. However, the best cutoff for the detection of non-CCR5 variants that most accurately predict responders to CCR5 inhibitors remains controversial. (25) Recent retrospective analyses have used G2P and a FPR <3.5% (see Table 3). The proportion of the viral population that can be detected as non-CCR5 for maraviroc treatment to remain effective has been established as 2% or less. (33) Other studies have also reported high concordance between deep sequencing and current tropism assays (22, 34) and between different sequencing platforms (35). The sample data in Table 3 suggest that deep sequencing performs similarly to ESTA and the original Trofile assay at predicting response to maraviroc treatment. Moreover, as noted by Swenson et al., the group of patients with 2–20% non-CCR5 virus according to deep sequencing had minority non-CCR5 variants that were not reliably detected by the original Trofile assay, but this group of patients had poor response to maraviroc, with 27% of the patients achieving virologic suppression at week 48, similar to the non-CCR5 group as a whole (26%) and to patients with >20% non-R5 virus (25%). (36) These results suggest that detection of minority non-CCR5 variants by deep sequencing may be important for predicting response. However, as cutoff values and specifics of the interpretation process are not yet standardized, (25) the clinical utility of deep sequencing remains to be shown,

Table 3. Performance of HIV V3 Deep Sequencing, Trofile, and ESTA Assays with Reference to Maraviroc Treatment Outcomes




RT-PCR Repli-cates

Virologic Response Definition

V3 Genotyping Algorithm

V3 Genotyping vs Virologic Response to MVC

Original Trofile vs Virologic Response to MVC

ESTA vs Virologic Response to MVC

Gonzalez-Serna 2011 (28)


Patients with persistent viral load and on treatment hiatus


<50 copies/mL or reduction >1 log on day 8

G2P clonal,






Swenson 2011 (37)


Drug-naïve patients from MERIT trial


<50 copies/mL at week 48

G2P clonal,


Sens=93% Spec=15%




Swenson 2011 (36)


Treatment-experienced patients from MOTIVATE and 1,029 studies


<50 copies/mL at week 48



[~90% concordance with G2P]

Sens=83% Spec=36%

Sens=93% Spec=17%



Based on the evidence from the clinical studies used for FDA approval, and the labeled requirement for tropism testing immediately prior to initiating a course of maraviroc, human immunodeficiency virus (HIV) tropism testing using the enhanced sensitivity version of the phenotypic Trofile assay is considered medically necessary for both treatment-experienced and treatment-naïve patients who are being considered for immediate treatment with maraviroc.

The evidence comparing HIV V3 population genotyping to original Trofile and enhanced sensitivity Trofile assay (ESTA), using maraviroc response as the reference for all assays, strongly suggests that genotyping is equivalent to Trofile assays in selecting patients likely to respond to maraviroc, the outcomes of interest. Studies evaluating genotyping and using paired ESTA results for reference suggest that genotyping may be somewhat less sensitive for detecting CXCR4-topic samples, but these studies were smaller, and most did not test in triplicate. Based largely on the maraviroc response results, HIV V3 population genotyping is considered medically necessary for patients considering immediate maraviroc treatment.

Either phenotyping or genotyping may be used to determine tropism when considering maraviroc treatment; both are not required.

Currently, patient management decisions are based on monitoring of CD4 cell counts and HIV plasma viral load. Studies would be needed to support improved outcomes with additional tropism monitoring during treatment. Pending such studies, tropism testing during treatment with co-receptor antagonists is investigational. In addition, data are not available to support the use of phenotypic tropism testing to predict prognosis, or to determine tropism in advance of a possible need for a regimen change to a co-receptor antagonist at a later date; accordingly, these indications are also investigational.

Finally, based on initial data, V3 deep sequencing (i.e. next generation sequencing) compared to ESTA or standard third variable (V3)-genotyping may identify additional patients who are unlikely to benefit from CCR5 inhibitor treatment. However, various aspects of the method are not yet standardized for this application and V3 deep sequencing for tropism determination is therefore investigational.

Practice Guidelines and Position Statements

The European Consensus Group on clinical management of tropism testing states that tropism testing is indicated for patients who fail treatment or have unacceptable toxicity and a CCR5 inhibitor is being considered. (24) In the absence of evidence, the group provides no guidance regarding tropism testing for newly diagnosed patients whose immediate treatment plan does not include a CCR5 inhibitor. In the absence of adequate data, the group could provide no guidance regarding the question of testing treatment-naïve patients prior to the start of a regimen not including a CCR5 inhibitor, in anticipation of need for a fast change to a CCR5 inhibitor due to the toxicity of the initial treatment regimen. For patients with a plasma HIV RNA load >1,000 copies/mL, tropism testing can be done by Trofile ESTA or by population genotypic analysis of the V3 loop, indicating for both a moderate level of evidence based on well-designed, nonrandomized trials or cohort studies with long-term clinical outcomes. For patients with a plasma HIV RNA load <1,000 copies/mL, genotyping is the preferred method.

The Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents states that tropism assays should be used whenever the use of a CCR5 inhibitor is being considered (based on strong evidence from randomized trials with clinical outcomes) and possibly for patients who exhibit virologic failure during CCR5 inhibitor treatment (optional recommendation based on expert opinion, no data cited). (9) Other uses of tropism assays, e.g., for prognostic purposes or in case use of a CCR5 inhibitor is needed later do not have sufficient data to support a recommendation. ESTA is recognized as the more sensitive version of the original assay used in the qualifying maraviroc clinical trials. Genotyping is noted as apparently less sensitive, but based on 2 “recent studies,” possibly as accurate as phenotyping in predicting response to treatment. However, these guidelines do not yet cite all the large, published studies summarized in Table 1; rather, citing uncertainty of the evidence, they recommend phenotyping as the preferred method of tropism testing.

Other published, relevant guidelines have not been recently updated and do not include the most recent evidence.

Medicare National Coverage



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CPT   See Policy Guidelines
ICD-9 diagnosis 042 Human immunodeficiency virus (HIV) disease
ICD-10-CM (effective 10/1/14) B20 Human immunodeficiency virus (HIV) disease
  Z21 Asymptomatic human immunodeficiency virus (HIV) disease status
ICD-10-PCS (effective 10/1/14)   Not applicable. ICD-10-PCS codes are only used for inpatient services. There are no ICD procedure codes for laboratory tests.
Type of Service   Laboratory/Pathology

Antiretroviral drug resistance testing
HIV coreeptor phenotyping

Policy History
Date Action Reason
12/13/07 Add to Medicine Section,Pathology/Laboratory section New policy
12/11/08 Replace policy  Policy updated with literature search through October 2008; reference numbers 9-12 added. No change to policy statements
12/10/09 Replace policy Policy updated with literature search through November 2009; reference numbers 1, 3, 4, 6, 14-16 added. Policy statements revised to include treatment-naïve patients as one of the indications that may be considered medically necessary
3/08/12 Replace policy Policy updated with literature review, references 3,5,9,10,17, 20-34 added. Policy statement added to indicate that HIV V3 genotyping is medically necessary for tropism testing.
03/14/13 Replace policy Policy updated with literature review through January 2013, references 25, 26, 28, 35-37 added. Policy statement unchanged.

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