Various general immune reconstitution inflammatory syndrome (IRIS) case definitions in HIV-infected patients had been published since 2004 [1–3]. However, a standardized clinical case definition for paradoxical tuberculosis-associated IRIS (TB-IRIS) primarily was lacking. The International Network for the Study of HIV-associated IRIS published criteria for paradoxical TB-IRIS and unmasking TB-IRIS diagnosis in 2008 (INSHI-2008 definition)  aimed for use in settings in which laboratory infrastructure is often limited. Briefly, INSHI case definition of IRIS includes diagnosis of TB, initial response to treatment, onset should be within 3 months of HAART initiation, and it should be combined with clinical criteria. To date, there has been no validation of this consensus case definition. Therefore, the objective of this prospective study was to assess performance of the INSHI-2008 definition and to study clinical manifestations of, and predictive factors for, paradoxical TB-IRIS among Thais coinfected with HIV-1 and TB in a clinical trial comparing pharmacokinetic measures between efavirenz and nevirapine, in patients who were receiving rifampicin .
Patients coinfected with HIV and TB who were receiving antituberculous therapy were enrolled between 2006 and 2007 and they were prospectively followed through 24 weeks after HAART. Inclusion criteria were HIV-infected individuals 18–60 years of age; active TB diagnosed by clinical features, positive acid-fast stain, and/or positive culture for Mycobacterium tuberculosis; treated with an antituberculous regimen 4–16 weeks prior to enrollment; naive to HAART; and CD4 cell count less than 350 cells/μl. Exclusion criteria were serum transaminase more than five times of upper limit of normal range; serum creatinine more than 2 mg/dl; receiving a medication that has drug–drug interactions with nevirapine or efavirenz; receiving immunosuppressive drugs; pregnancy or lactation; and the culture results yielded nontuberculous mycobacteria. Directly observed therapies were implemented.
Extrapulmonary TB included TB that involved lymph node, pleura, gastrointestinal tract, or others. Disseminated TB is defined as military TB or TB that involved more than one organ or positive blood culture for M. tuberculosis. Tests other than chest X-ray were performed when the clinical signs and symptoms suggested IRIS; they were not routinely done in all cases. The anti-TB regimen consisted of isoniazid, rifampicin, ethambutol, and pyrazinamide for the first 2 months followed by isoniazid and rifampicin for the subsequent 4 months. All patients were started on stavudine, lamivudine, and either efavirenz 600 mg/day at bedtime or nevirapine 200 mg twice a day. Two definitions in the present study included ‘study definition’ and ‘INSHI-2008 definition’. In terms of study definition, patients were classified as having definite TB-IRIS if they met two major criteria, or met criterion A of the major criteria and two minor criteria from a case definition previously described by French et al.  with confirmation by an independent external reviewer. Patients who did not meet all of the criteria for definite TB-IRIS but who were considered by the external reviewer to have clinical manifestations consistent with the syndrome were classified as having possible TB-IRIS. The cases were later compared by the classification using the INSHI-2008 consensus definition . Clinical events at weeks 6, 12, and 24 and at time of TB-IRIS were recorded. All patients were instructed to report by phone call and present to the hospital for any atypical symptoms. Clinical assessment, including complete physical examination, laboratory, and radiological investigations, was performed to exclude alternative diagnoses. CD4 cell count by flow cytometry and plasma HIV-1 RNA using Roche Amplicor version 1.5 (Roche Diagnostics, Branchburg, New Jersey, USA) were assessed at baseline and every 12 weeks thereafter. Medication adherence was assessed by questionnaire.
All statistical analyses were performed using SAS software, version 9.1 (SAS Institute, Cary North Carolina, USA). Sensitivity, specificity, positive predictive value, and negative predictive value of the INSHI-2008 definition compared with the study definition were shown using the Wilson score method. The chance-corrected proportional agreement (Kappa coefficient) was calculated. Student's t-test was used for analysis of continuous data with parametric distributions, whereas the Wilcoxon rank sum test was used for analysis of nonparametric data. Categorical data were analyzed using the χ2 test. Possible predictive factors for TB-IRIS were evaluated with a logistic regression model by adjusting for confounding factors with a P value less than 0.2 from univariate analysis. A two-sided α less than 0.05 was considered to indicate statistical significance. The institutional ethics committees of the Bamrasnaradura Infectious Diseases Institute and the Thai Ministry of Public Health approved the study. All patients provided written, informed consent. This clinical trial is registered in the National Library of Medicine's registry under the registration number NCT00483054.
Of 142 patients who were initially enrolled, 16 patients were excluded: cultures revealed growth of nontuberculous mycobacteria in 12 patients and four were excluded due to other causes. The remaining 126 patients were included in the final analysis. The median [interquartile range (IQR)] age was 35 (31–42) years and 66% were men. A majority had TB confirmed either by acid-fast stain and/or culture as follows: 79 (62.7%) patients had a positive acid-fast stain and 66 (52.4%) had culture confirmation. Median (IQR) baseline CD4 cell count was 43 (23.0–92.0) cells/μl and median (IQR) HIV-1 RNA was 5.9 (5.5–6.0) log10 copies/ml. Fifty-three (42%) patients were diagnosed as having pulmonary TB, 45 (36%) had disseminated TB, and 28 (22%) had extrapulmonary TB. Median (IQR) time between antituberculous regimens and HAART initiation was 1.5 (1.2–2.3) months. Of 126 patients, 22 (18%) patients fulfilled TB-IRIS criteria by study definition. Sixteen of 22 patients had definite TB-IRIS and six of 22 patients had possible TB-IRIS. Overall, 21 (17%) patients fulfilled TB-IRIS criteria by the INSHI-2008 definition. Table 1 shows percentages and 95% confidence intervals (CIs) of each value by INSHI-2008 definition. Common manifestations of TB-IRIS were as follows: 73% lymph node enlargement, 59% fever, 36% cough, 18% abdominal pain, and 18% headache. Eighteen (82%) patients had worsening of a preexisting site, whereas four (18%) had TB-IRIS in a new location. Median (IQR) time between HAART initiation and TB-IRIS development was 14 (9–18) days. Of 22 patients, 14, five, two, and one patients developed TB-IRIS after 2, 4, 6, and 8 weeks of HAART, respectively. By INSHI-2008 definition, 14, four, two, and one patients developed TB-IRIS after the corresponding number of weeks.
Of the three patients with discordant TB-IRIS diagnosis, two patients who met criteria of ‘study definition’ but did not meet criteria of ‘INSHI-2008’ were one patient with smear-positive cervical lymphadenitis having no markedly recurrent lymphadenitis or other manifestation that met the major criteria of INSHI-2008 and another patient with smear-positive pulmonary TB who did not meet any major criteria of INSHI because of no clear documentation of node enlargement. One patient with disseminated TB met criteria of ‘INSHI-2008’ but did not meet criteria of ‘study definition’ because the CD4 cell count decreased from baseline of less than 25 cells/μl and HIV-1 RNA decreased from baseline of less than 1 log10 copies/ml.
Median CD4 cell responses of patients who developed TB-IRIS vs. non-TB IRIS at baseline, week 12, and week 24 were 35 vs. 44 cells/μl, 174 vs. 156 cells/μl, 188 vs. 168 cells/μl, respectively (all P > 0.05). Median increase in CD4 cell count at week 12 from baseline (144 vs. 91 cells/μl) and at week 24 from baseline (137 vs. 118 cells/μl) between the corresponding groups were not different (P > 0.05). Plasma HIV-1 RNA was not different at three time points and decrease in plasma HIV-1 RNA from baseline between patients with and without TB-IRIS did not differ (all P > 0.05). Table 2 shows factors that predicted paradoxical TB-IRIS. Six patients died. All causes of death were unrelated to TB-IRIS.
Overall, high concordance between the INSHI-2008 definition and the study definition by French 2004 for TB-IRIS diagnosis was beyond what would have been expected by chance (Kappa 0.918). Moreover, the INSHI-2008 definition also had high performance with regard to its sensitivity and specificity in these particular patients with high pretest probability. With low numbers of false-positive and false-negative cases, a case fulfilled INSHI-2008 definition is in itself good for the diagnosis of paradoxical TB-IRIS. Nevertheless, optimal monitoring should include CD4 cell count and HIV-1 RNA and these measurements should be assessed when considering the diagnosis of TB-IRIS. In case they are not available, the INSHI definition provides a reasonable alternative in establishing the diagnosis.
Two patients were diagnosed by study definition only. Interestingly, these differences were mainly due to the patients not developing obvious focal inflammation at the initial site of TB or even another new inflammatory anatomic site except exaggerated high fever after excluding other causes. However, exaggerated inflammatory reaction, that is, marked fever, is considered to be a major criterion in the study definition based on French 2004. Patients with TB-IRIS might present with high fever and subtle focal inflammatory reaction. Therefore, patients in this category may be missed when the INSHI-2008 definition is applied. On the other hand, one patient was diagnosed with paradoxical TB-IRIS by INSHI-2008 only. This can be explained by the immunological and virological responses not meeting the study definition. Another observation was that no IRIS cases occurred beyond 2 months of HAART initiation. Paradoxical TB-IRIS after 3 months has been infrequently reported so far [6,7]. Hence, inclusion of a timeframe of the first 3 months of HAART, which corresponds to the period of rapid immune recovery , is reasonable. Moreover, the results derived from INSHI-2008 are also consistent with findings from study definition in terms of risk factor identification and the strength of association.
The IRIS rate in this cohort is similar to that of other reports from resource-constrained countries, which ranged from 8 to 13% [6,7,9] compared with 17 to 43% from resource-rich countries [10–14]. The median time between HAART initiation and TB-IRIS development was 2 weeks. This number corresponds to those in other reports [10,13,14], but it is slightly higher than that in our own previous report . The explainable reason is the earlier initiation of HAART in this study. A number of risk factors associated with TB-IRIS have been identified previously . The present study demonstrated that ‘extrapulmonary TB’ and ‘disseminated TB’ were independently associated with TB-IRIS with the odds ratio of 4–9. This finding is consistent with previous report  and may reflect a high pathogen load. Finally, none of the patients in the study died from an IRIS event. To date, death has been reported infrequently [4,6,7,11,15].
A number of limitations should be acknowledged. First, the performance of definition can change if the population tested is dramatically different from ours. Second, this study incorporated a definition based on the French 2004 criteria and the decision of an independent external reviewer. Further studies may apply different standard criteria to appraise INSHI-2008. Third, our sample size may not be large enough to detect some previous documented risk factors. Ultimately, current treatment guidelines support the coadministration of rifampicin with efavirenz-based over nevirapine-based regimens because of lesser drug–drug interactions and high efficacy. However, the difference in HAART regimen was not found to be associated with TB-IRIS.
In resource-constrained countries, physicians treat advanced HIV-infected patients with TB in the setting of limited laboratory capacity. Herein, we demonstrated the validity of a recently published clinical case definition to define paradoxical TB-IRIS. This suggests that lack of laboratory tools does not impede the ability to diagnose TB-IRIS.
The authors wish to thank all the patients in the study as well as Dr Preecha Tantanathip, Dr Achara Chaovavanich, Dr Somsit Tansuphaswadikul, Dr Palakorn Srinithiwat, Supeda Thongyen, Samruay Nilkamhang, Phatchara Tunteerapat, Putthiporn Limpanadusadee, Samroui Kaewsaard, and all other staff in Bamrasnaradura Infectious Diseases Institute for their support and assistance in conducting the study. This study was funded by a grant from the Ministry of Public Health, Thailand; The Thailand Research fund (TRF); and Bamrasnaradura Infectious Diseases Institute, Thailand.
All authors declare no conflicts.
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