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Dual-Time Point Whole-Body 18F-Fluorodeoxyglucose PET/CT Imaging in Undiagnosed Mediastinal Lymphadenopathy18F FDG PET/CT Scan: Sarcoidosis and TB: A Prospective Study of 117 Patients With Sarcoidosis and TB FREE TO VIEW

Venkata Nagarjuna Maturu, MD, DM; Ritesh Agarwal, MD, DM, FCCP; Ashutosh Nath Aggarwal, MD, DM, FCCP; Bhagwant Rai Mittal, MD, DNB; Amanjit Bal, MD, DNB; Nalini Gupta, MD, DNB; Dheeraj Gupta, MD, DM, FCCP
Author and Funding Information

From the Department of Pulmonary Medicine (Drs Maturu, Agarwal, Aggarwal, and D. Gupta), Department of Nuclear Medicine (Dr Mittal), Department of Histopathology (Dr Bal), and Department of Cytology and Gynaecological Pathology (Dr N. Gupta), Postgraduate Institute of Medical Education and Research.

CORRESPONDENCE TO: Dheeraj Gupta, MD, DM, FCCP, Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh-160012, India; e-mail: dheeraj1910@gmail.com


FINANCIAL/NONFINANCIAL DISCLOSURES: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;146(6):e216-e220. doi:10.1378/chest.14-1827
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Published online
To the Editor:

Sarcoidosis and TB, the two most common benign causes of mediastinal lymphadenopathy, share remarkable clinical, radiologic, and histologic similarities.1 Differentiation between the two remains a difficult task for pulmonary physicians, particularly in countries with a high burden of TB.2 We performed a dual-time point 18F-fluorodeoxyglucose (FDG) PET/CT scan in 117 consecutive patients with undiagnosed mediastinal lymphadenopathy (Table 1). The study was approved by the Ethics Review Committee (No. 1TRG/PG-2012/20234-58) of our institution, and written informed consent was obtained from all subjects. A final diagnosis of TB (n = 29) or sarcoidosis (n = 88) was made at 6 months follow-up based on clinical response to the treatment (Fig 1).

Table Graphic Jump Location
TABLE 1 ]  Inclusion and Exclusion Criteria, Procedures, and Definitions

ATT = anti-TB therapy; FDG = fluorodeoxyglucose; SUVmax = maximum standardized uptake value; TST = tuberculin skin test.

Figure Jump LinkFigure 1 –  CONSORT (Consolidated Standards of Reporting Trials) diagram of the patients in this study. AFB = acid-fast bacillus; FDG = fluorodeoxyglucose.Grahic Jump Location

The baseline clinical and demographic parameters are shown in Table 2. The pattern of FDG uptake in various lymph node groups of the body, percentage of patients with pulmonary parenchymal FDG positivity (sarcoidosis, 52.3%; TB, 44.8%), and patterns of FDG uptake in the lung parenchyma and by extrapulmonary organs (sarcoidosis, 40.9%; TB, 41.3%) were similar between the two study groups (Table 3). FDG uptake was most frequent in the lower paratracheal lymph node (station 4) (sarcoidosis, 98.9%; TB, 96.6%) and the subcarinal lymph node (station 7) (sarcoidosis, 94.3%; TB, 93.1%). Among the mediastinal nodal stations, FDG uptake in the paraaortic (63.6% vs 28.6%, P = .0001) and interlobar (83% vs 55.2%, P = .002) lymph nodes was more common in sarcoidosis. The median maximum standardized uptake value (SUVmax) (early), SUVmax (delayed), and retention index (RI) were 12.4, 16.2, and 32.3%, respectively, in the sarcoidosis group and 10.9, 14.4, and 33.8%, respectively, in the TB group. Patients with sarcoidosis more often had SUVmax (early) values > 15.0 (31 patients vs four patients, P = .026). An SUVmax (early) cutoff of 15.0 for identifying sarcoidosis has a specificity of 86.2% and positive predictive value of 88.6%. Thus, in a patient suspected of having either TB or sarcoidosis, a finding of SUVmax (early) > 15.0 increases the probability of it being sarcoidosis. However, this cutoff has poor sensitivity and negative predictive values of 35.6% and 30.9%, respectively.

Table Graphic Jump Location
TABLE 2 ]  Demographic and Clinical Characteristics of the Study Population

Data are presented as No. (%) or mean ± SD. ESR = erythrocyte sedimentation rate. See Table 1 legend for expansion of other abbreviation.

a 

Significant at P < .01.

Table Graphic Jump Location
TABLE 3 ]  FDG Uptake Patterns and Intensity of Uptake in the Study Population

Data are presented as No. (%) or median (interquartile range). See Table 1 legend for expansion of abbreviations.

a 

Peripheral groups include cervical, supraclavicular, axillary, and inguinal nodes.

In this study, 115 (98.3%) and 100 (85.5%) patients had SUVmax (early) values > 2.5 and > 6.2, respectively; hence, these cutoffs cannot be used for differentiating benign from malignant lesions, as proposed earlier.3 Additionally, all except three patients had a positive RI, and 85 patients (72.6%) had an RI of > 20%. These findings challenge the earlier proposed role of dual-time point PET imaging in differentiating benign from malignant lesions.4,5 This study is the first to our knowledge to compare FDG-PET findings between sarcoidosis and TB, and the results suggest the futility of this modality in differentiating between the two.

References

Gupta D, Agarwal R, Aggarwal AN, Jindal SK. Sarcoidosis and tuberculosis: the same disease with different manifestations or similar manifestations of different disorders. Curr Opin Pulm Med. 2012;18(5):506-516. [CrossRef] [PubMed]
 
Dhooria S, Agarwal R, Aggarwal AN, Bal A, Gupta N, Gupta D. Differentiating tuberculosis from sarcoidosis by sonographic characteristics of lymph nodes on endobronchial ultrasonography: a study of 165 patients. J Thorac Cardiovasc Surg. 2014;148(2):662-667. [CrossRef] [PubMed]
 
Kumar A, Dutta R, Kannan U, Kumar R, Khilnani GC, Gupta SD. Evaluation of mediastinal lymph nodes using F-FDG PET-CT scan and its histopathologic correlation. Ann Thorac Med. 2011;6(1):11-16. [CrossRef] [PubMed]
 
Kadaria D, Archie DS, SultanAli I, Weiman DS, Freire AX, Zaman MK. Dual time point positron emission tomography/computed tomography scan in evaluation of intrathoracic lesions in an area endemic for histoplasmosis and with high prevalence of sarcoidosis. Am J Med Sci. 2013;346(5):358-362. [CrossRef] [PubMed]
 
Shinya T, Rai K, Okumura Y, et al. Dual-time-point F-18 FDG PET/CT for evaluation of intrathoracic lymph nodes in patients with non-small cell lung cancer. Clin Nucl Med. 2009;34(4):216-221. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1 –  CONSORT (Consolidated Standards of Reporting Trials) diagram of the patients in this study. AFB = acid-fast bacillus; FDG = fluorodeoxyglucose.Grahic Jump Location

Tables

Table Graphic Jump Location
TABLE 1 ]  Inclusion and Exclusion Criteria, Procedures, and Definitions

ATT = anti-TB therapy; FDG = fluorodeoxyglucose; SUVmax = maximum standardized uptake value; TST = tuberculin skin test.

Table Graphic Jump Location
TABLE 2 ]  Demographic and Clinical Characteristics of the Study Population

Data are presented as No. (%) or mean ± SD. ESR = erythrocyte sedimentation rate. See Table 1 legend for expansion of other abbreviation.

a 

Significant at P < .01.

Table Graphic Jump Location
TABLE 3 ]  FDG Uptake Patterns and Intensity of Uptake in the Study Population

Data are presented as No. (%) or median (interquartile range). See Table 1 legend for expansion of abbreviations.

a 

Peripheral groups include cervical, supraclavicular, axillary, and inguinal nodes.

References

Gupta D, Agarwal R, Aggarwal AN, Jindal SK. Sarcoidosis and tuberculosis: the same disease with different manifestations or similar manifestations of different disorders. Curr Opin Pulm Med. 2012;18(5):506-516. [CrossRef] [PubMed]
 
Dhooria S, Agarwal R, Aggarwal AN, Bal A, Gupta N, Gupta D. Differentiating tuberculosis from sarcoidosis by sonographic characteristics of lymph nodes on endobronchial ultrasonography: a study of 165 patients. J Thorac Cardiovasc Surg. 2014;148(2):662-667. [CrossRef] [PubMed]
 
Kumar A, Dutta R, Kannan U, Kumar R, Khilnani GC, Gupta SD. Evaluation of mediastinal lymph nodes using F-FDG PET-CT scan and its histopathologic correlation. Ann Thorac Med. 2011;6(1):11-16. [CrossRef] [PubMed]
 
Kadaria D, Archie DS, SultanAli I, Weiman DS, Freire AX, Zaman MK. Dual time point positron emission tomography/computed tomography scan in evaluation of intrathoracic lesions in an area endemic for histoplasmosis and with high prevalence of sarcoidosis. Am J Med Sci. 2013;346(5):358-362. [CrossRef] [PubMed]
 
Shinya T, Rai K, Okumura Y, et al. Dual-time-point F-18 FDG PET/CT for evaluation of intrathoracic lymph nodes in patients with non-small cell lung cancer. Clin Nucl Med. 2009;34(4):216-221. [CrossRef] [PubMed]
 
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