CD4+ T-lymphocyte count is the strongest predictor of disease progression in HIV-infected patients, and prophylaxis of opportunistic infection is recommended when it drops below 200 cells/μL.1–6 Frequent CD4+ cell count monitoring has been highly recommended for many years, but the utility of monitoring has been recently debated.7,8 In HIV-infected people receiving antiretroviral therapy (ART), CD4+ counts tend to increase or remain stable as long as viral replication is controlled,9–12 and clinical events very infrequently occur after ART introduction.10,13 Furthermore, there are no treatment strategies to increase CD4+ cell count during periods of viral suppression. A CD4+ count drop below 200 cells/μL is currently seldom observed during successful ART,14–17 and frequent testing may cause unnecessary anxiety in patients with clinically inconsequential fluctuations. Therefore, the utility of their monitoring has become a matter of debate.7,8,17 Indeed, the treatment decision a clinician can take in response to CD4+ monitoring is to start (or restart) prophylaxis of opportunistic infections when counts drop below 200 cells/μL1–4 or, in clinical settings where viral load testing is not routinely implemented, to prescribe viral load testing.18 In this context, some guidelines recommend optional or stop monitoring CD4+ cell counts once virological suppressions (VS) are sustained, and the immunological status is stabilized.1,3,18
There are no randomized comparisons of individuals following different CD4+ count monitoring strategies as they are difficult to be performed, and although it is well established that CD4+ cells falling below 200 cells/μL occur infrequently while viral load is suppressed,14–17,19 robust estimates of CD4+ cells dropping below 200 cells/μL over long follow-up are limited. Furthermore, relevant differences might emerge when comparing data collected in countries with different organizations of the social health system.
The aim of this analysis was to quantify the probability of a drop in CD4+ counts below 200 cells/μL after reaching values >350 cells/μL on ART (or when starting ART with CD4+ count >350 cells/μL) in the absence of virological failure (VF), in a cohort of Italian HIV-infected patients.
The ICONA Foundation Study (ICONA) is a multicenter prospective observational study of HIV-1–infected adult patients, which was set up in 1997. Eligible patients are those starting ART when they are naive to antiretrovirals, regardless of the reason. The ICONA Foundation Study has been approved by IRB of all the participating centers; sensitive data from patients are seen only in aggregate form. All patients signed a consent form to participate in ICONA, in accordance with the ethical standards of the committee on human experimentation and the Helsinki Declaration (1983 revision). Demographic, clinical and laboratory data, and information on therapy are collected for all participants and recorded using electronic data collection [www.icona.org].
CD4+ monitoring in cohort participants is performed at least twice yearly, according to the study protocol and the Italian guidelines.2 Antiretroviral regimens used by the studied patients were not predefined by the study protocol (which is strictly observational) but were prescribed according to the current Italian guidelines.2
VS was defined as having achieved on 2 consecutive occasions a viral load ≤50 copies/mL. Participants could be included in this analysis if they belonged to 2 distinct inclusion criteria group: first, participants who started ART with a CD4+ count >350 cells/μL; second, participants who started ART with ≤350 CD4+/μL, achieved VS on therapy and whose CD4+ count subsequently increased to a value >350 cells/μL. In patients who started ART with >350 CD4+/μL, baseline was defined as the date of VS after at least 6 months since initiation of ART. In those who started ART with ≤350 CD4+/μL, baseline was the date of first achieving a CD4+ value >350 CD4+/μL after VS. For both groups, we insisted on people to have at least 1 VL and CD4+ count assessed after baseline.
Viral load was assessed in each center according to local procedures. Yearly change in CD4+ cell counts after baseline were estimated by fitting a linear mixed model with random intercept and slope.
The primary end point was the cumulative risk of a confirmed CD4+ drop below 200 cells/μL over follow-up, defined as 2 consecutive counts below 200 cells/μl (confirmed drop). We also evaluated a secondary end point defined using a single count below 200 cells/μL (unconfirmed drop). Participants' time at risk was censored at the date of VF (defined as a confirmed HIV-RNA >50 copies/mL), death, or last clinical visit. The Kaplan–Meier method was used to estimate the cumulative risk of CD4+ dropping below 200 cells/μL over time. The 97.5% upper limit of the confidence interval (CI) was calculated using a normal approximation. All analyses were repeated also using an alternative definition of viral rebound (with a cutoff of 400 copies/mL instead of 50 copies/mL).
All analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).
Six thousand six hundred sixty-three adult patients were included in the analysis (Table 1). The main differences between patients who started ART with <350 CD4+/μL and those who started ART with >350 CD4+/μL regarded sex, risk factor, nationality, CD4+ nadir, CD4+/CD8+ ratio, hepatitis C virus co-infection, and HIV-RNA load.
Over a median (Q1, Q3) follow-up of 45 (21, 89) months, new AIDS-defining events occurred in 124 (2%) patients, serious non-AIDS defining20 in 306 (5%), death in 153 (2%; 21 AIDS related, 132 non-AIDS related), and VF in 1796 (27%). The median (Q1, Q3) CD4+ count at the time the AIDS-defining events occurred was 458 (228, 671) cells/μL.
The median (interquartile range) CD4+ measurements over follow-up was 5 (2, 12), for an average of 2.6 (2.0, 3.4) measurements per year, and the median of prospective HIV-RNA measurements was also 5 (2, 11), for 2.6 (2.0, 3.4) measurements per year.
Baseline CD4+ cell count was 646 (611, 682)/μL in patients who started ART with ≤350 CD4+/μL and 757 (708, 807)/μL in those who started ART with >350 CD4+/μL [difference: 110.9 (95% CI: 50.4 to 171.5) cells/μL; P < 0.001]. Estimated yearly changes in CD4+ cell counts were +27.44 (-18.2, +73.12) cells/μL in patients who started ART with ≤350 CD4+/μL and +31.99 (-8.83, +72.81) cells/μL in those who started ART with >350 CD4+/μL [difference: +4.55 (-56.5, +65.64) cells/μL; P = 0.884] (Supplemental Digital Content Figure, http://links.lww.com/QAI/B72).
A confirmed CD4+ drop below 200 cells/μL was never observed over the time of the study; unconfirmed CD4+ drops below 200 cells/μL occurred in 9 patients, and no clinical events were observed at the time of occurrence. The Kaplan–Meier estimate of the cumulative risk of unconfirmed drop below 200 cells/μL was 0.24% (95% CI: 0.07 to 0.40) by 4 years from baseline; no further events were observed over the following 9 years, and 249 individuals were still at risk by 12 years after baseline. Upper limits of the 97.5% CI of rates of confirmed CD4+ drop below 200 cells/μL were 0.28 and 0.38/1000 person-years of follow-up (PYFU) for patients with ≤350 and >350 CD4+ cells/μL at ART start, respectively. Upper limits of the 97.5% CI of rates of confirmed CD4+ drop below 200 cells/μL according to type of ART started, hepatitis C virus co-infection, calendar year of baseline, baseline CD4/CD8 >0.3 or ≤0.3, and time from HIV diagnosis and HIV-RNA at ART start > or ≤5 log10 copies/mL are shown in Table 2. Of note, all these upper limits were below 2.0 per 1000 PYFU. Only patients with calendar year baseline between 1997 and 2001 and those with a CD4+/CD8+ ≤0.3 at ART start had an upper limit that was >1 per 1000 PYFU. Results were similar when viral rebound was defined using the more conservative threshold of 400 copies/mL for the definition of VF (data not shown).
We investigated the risk of CD4+ drop below 200 cells/μL in patients who started ART with >350 CD4+ cells/μL or reached >350 CD4+ cells/μL after VS, and no events drop was observed over a median follow-up of approximately 4 years, as long as VS was maintained. Even in the worst case scenario, in which the true value for the incidence is equal to the upper limit of the 97.5% of the CI, this incidence of a drop <200 cells/μL was between 1 and 2 per 1000 PYFU. This estimate is consistent with that previously found elsewhere. In another analysis of a cohort of 1820 HIV-infected patients, those with HIV-1 RNA <200 copies/mL and CD4+ counts ≥300 cells/μL had a 97% probability of maintaining durable CD4+ counts ≥200 cells/μL for 4 years.14 Similarly, in the ARTEMIS trial, only 1% of 449 patients with sustained HIV-1 RNA suppression below 400 copies/mL experienced a CD4+ count drop below 200 cells/μL on 2 consecutive visits.15 In 7250 patients in South Africa, after 10 years of ART, 93% of patients with ongoing VS maintained CD4+ cell counts continuously above 200 cells/μL.19 Furthermore, in an Asian cohort, among 1538 patients virologically suppressed over an unreported duration of follow-up, the rate of a confirmed drop below 200 CD4+/μL was 0.77/100 person-years. There was no significant difference in the time to a confirmed drop below 200 CD4+/μL when comparing people who were monitored biannually vs. those who had annual CD4+ measurements.21 Finally, in the PISCIS Cohort Study, over a median follow-up of almost 2 years, CD4+ cell counts fell to <200 cells/μL in 7% of 8695 patients.16 However, this estimate was calculated counting also single measurements below 200 CD4+/μL.
It can be argued that experiencing a CD4+ count drop below 200 cells/μL might not be clinically relevant, because clinical events typically occur also with counts of >200 cells/μL. Of interest, nevertheless, in 39,283 HIV-infected patients with VL <1000 copies/mL or CD4+ cell counts ≥350/μL in the resource-limited setting, the implementation of routine CD4+ cell count monitoring beyond 12 months after ART initiation did not seem to have an impact on long-term mortality rates.13
It needs to be considered that frequent monitoring of CD4+ count in the setting of well-controlled viral replication might be only a source of patients' anxiety as the result of the test is unlikely to trigger treatment decision7,8; reducing the frequency of CD4+ monitoring might also reduce the overall costs related to care of HIV-infected patients.8,17 However, knowing when CD4+ drop below 200 cells/μL is important, because in these cases (re)starting prophylaxis of opportunistic infections is recommended.1–4 In the absence of randomized comparisons of CD4+ count monitoring strategies, our analysis provides solid estimates that should help designing such studies.
Caniglia et al recently tried to emulate a trial comparing the effect of different frequencies of CD4+ cell counts monitoring for clinical outcome using the data of a very large cohort. Most of the 39,029 cohort participants who were eligible for the comparison changed strategy during follow-up (mostly in the first 6 months); indeed, less than 1/10 of them did not change the initial strategy and could be maintained in the analysis over 2 years of follow-up, thus largely limiting the power of the study.10
The results of our analysis confirm and expand, over a long follow-up and in a setting where there is universal access to treatment, the results of previous analyses. They also lend support to optional monitoring of CD4+ cell counts in patients with satisfactory virological and immunological response to ART.
As participants' follow-up time was censored at VF, the results of this study are applicable only to the population of HIV-infected individuals with current stable VS. It must be noted that results also do not apply to immunological nonresponders. Indeed, people who started ART with ≤350 CD4+/μL and never attained values >350 cells/μL were excluded from the analysis because less frequent CD4+ cell counts monitoring is not an option in these patients.
The main limitations of this study are the relatively small sample size and the relatively short duration of follow-up; however, all events occurred over the first 3 years, so it is unlikely that results will be different by repeating the analysis after waiting for further follow-up to cumulate.
In summary, in patients who started ART in Italy with >350 CD4+ cells/μL, or reached >350 CD4+ cells/μL after VS, with a stable controlled viral suppression, a confirmed CD4+ drop below 200 cells/μL was never observed over an average of 4 years. The results of this study support optional monitoring of CD4+ cell counts, in a setting in which viral load assessment is easily available and in patients with these characteristics; they are also useful to help designing randomized trials comparing CD4+ count monitoring strategies in virologically suppressed populations.
Icona Foundation Study Group: Board of Directors: A d'Arminio Monforte (Vice-President), M Andreoni, G Angarano, A Antinori, F Castelli, R Cauda, G Di Perri, M Galli, R Iardino, G Ippolito, A Lazzarin, CF Perno, F von Schloesser, and P Viale. Scientific Secretary: A d’Arminio Monforte, A Antinori, A Castagna, F Ceccherini-Silberstein, A Cozzi-Lepri, E Girardi, S Lo Caputo, C Mussini, and M Puoti. Steering Committee: M Andreoni, A Ammassari, A Antinori, C Balotta, A Bandera, P Bonfanti, S Bonora, M Borderi, A Calcagno, L Calza, MR Capobianchi, A Castagna, F Ceccherini-Silberstein, A Cingolani, P Cinque, A Cozzi-Lepri, A d’Arminio Monforte, A De Luca, A Di Biagio, E Girardi, N Gianotti, A Gori, G Guaraldi, G Lapadula, M Lichtner, S Lo Caputo, G Madeddu, F Maggiolo, G Marchetti, S Marcotullio, L Monno, C Mussini, S Nozza, M Puoti, E Quiros Roldan, R Rossotti, S Rusconi, MM Santoro, A Saracino, and M Zaccarelli. Statistical and Monitoring Team: A Cozzi-Lepri, I Fanti, L Galli, P Lorenzini, A Rodano, M Shanyinde, and A Tavelli. Biological Bank INMI: F Carletti, S Carrara, A Di Caro, S Graziano, F Petrone, G Prota, S Quartu, and S Truffa. Participating Physicians and Centers: Italy A Giacometti, A Costantini, C Valeriani (Ancona); G Angarano, L Monno, C Santoro (Bari); F Maggiolo, C Suardi (Bergamo); P Viale, V Donati, G Verucchi (Bologna); F Castelli, E Quiros Roldan, C Minardi (Brescia); T Quirino, C Abeli (Busto Arsizio); PE Manconi, P Piano (Cagliari); B Cacopardo, B Celesia (Catania); J Vecchiet, K Falasca (Chieti); L Sighinolfi, D Segala (Ferrara); F Mazzotta, F Vichi (Firenze); G Cassola, C Viscoli, A Alessandrini, N Bobbio, G Mazzarello (Genova); C Mastroianni, V Belvisi (Latina); P Bonfanti, I Caramma (Lecco); A Chiodera, AP Castelli (Macerata); M Galli, A Lazzarin, G Rizzardini, M Puoti, A d’Arminio Monforte, AL Ridolfo, R Piolini, A Castagna, S Salpietro, L Carenzi, MC Moioli, C Tincati, G Marchetti (Milano); C Mussini, C Puzzolante (Modena); A Gori, G Lapadula (Monza); N Abrescia, A Chirianni, G Borgia, F Di Martino, L Maddaloni, I Gentile, R Orlando (Napoli); F Baldelli, D Francisci (Perugia); G Parruti, T Ursini (Pescara); G Magnani, MA Ursitti (Reggio Emilia); R Cauda, M Andreoni, A Antinori, V Vullo, A Cristaudo, A Cingolani, G Baldin, S Cicalini, L Gallo, E Nicastri, R Acinapura, M Capozzi, R Libertone, S Savinelli, A Latini (Roma); M Cecchetto, F Viviani (Rovigo); MS Mura, G Madeddu (Sassari); A De Luca, B Rossetti (Siena); P Caramello, G Di Perri, GC Orofino, S Bonora, M Sciandra (Torino); M Bassetti, A Londero (Udine); G Pellizzer, and V Manfrin (Vicenza).
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