Chest Radiograph Screening for Detecting Subclinical Tuberculosis in Asymptomatic Household Contacts, Peru.

The World Health Organization's end TB strategy promotes the use of symptom and chest radiograph screening for tuberculosis (TB) disease. However, asymptomatic early states of TB beyond latent TB infection and active disease can go unrecognized using current screening criteria. We conducted a longitudinal cohort study enrolling household contacts initially free of TB disease and followed them for the occurrence of incident TB over 1 year. Among 1,747 screened contacts, 27 (52%) of the 52 persons in whom TB subsequently developed during follow-up had a baseline abnormal radiograph. Of contacts without TB symptoms, persons with an abnormal radiograph were at higher risk for subsequent TB than persons with an unremarkable radiograph (adjusted hazard ratio 15.62 [95% CI 7.74-31.54]). In young adults, we found a strong linear relationship between radiograph severity and time to TB diagnosis. Our findings suggest chest radiograph screening can extend to detecting early TB states, thereby enabling timely intervention.

PET-CT-guided characterisation of progressive, preclinical tuberculosis infection and its association with low-level circulating Mycobacterium tuberculosis DNA in household contacts in Leicester, UK: a prospective cohort study.

BACKGROUND: Incipient tuberculosis, a progressive state of Mycobacterium tuberculosis infection with an increased risk of developing into tuberculosis disease, remains poorly characterised. Animal models suggest an association of progressive infection with bacteraemia. Circulating M tuberculosis DNA has previously been detected in pulmonary tuberculosis by use of Actiphage, a bacteriophage-based real-time PCR assay. We aimed to investigate whether serial [18F]fluorodeoxyglucose ([18F]FDG)-PET-CT could be used to characterise the state and progressive trajectory of incipient tuberculosis, and examine whether these PET-CT findings are associated with Actiphage-based detection of circulating M tuberculosis DNA. METHODS: We did a prospective 12-month cohort study in healthy, asymptomatic adults (aged ≥16 years) who were household contacts of patients with pulmonary tuberculosis, and who had a clinical phenotype of latent tuberculosis infection, in Leicester, UK. Actiphage testing of participants' blood samples was done at baseline, and [18F]FDG PET-CT at baseline and after 3 months. Baseline PET-CT features were classified as positive, indeterminate, or negative, on the basis of the quantitation (maximum standardised uptake value [SUVmax]) and distribution of [18F]FDG uptake. Microbiological sampling was done at amenable sites of [18F]FDG uptake. Changes in [18F]FDG uptake after 3 months were quantitatively categorised as progressive, stable, or resolving. Participants received treatment if features of incipient tuberculosis, defined as microbiological detection of M tuberculosis or progressive PET-CT change, were identified. FINDINGS: 20 contacts were recruited between Aug 5 and Nov 5, 2020; 16 of these participants had a positive result on IFNγ release assay (QuantiFERON-TB Gold Plus [QFT]) indicating tuberculosis infection. Baseline PET-CT scans were positive in ten contacts (all QFT positive), indeterminate in six contacts (three QFT positive), and negative in four contacts (three QFT positive). Four of eight PET-CT-positive contacts sampled had M tuberculosis identified (three through culture, one through Xpert MTB/RIF Ultra test) from intrathoracic lymph nodes or bronchial wash and received full antituberculosis treatment. Two further unsampled PET-CT-positive contacts were also treated: one with [18F]FDG uptake in the lung (SUVmax 9·4) received empirical antituberculosis treatment and one who showed progressive [18F]FDG uptake received preventive treatment. The ten untreated contacts with [18F]FDG uptake at baseline (seven QFT positive) had stable or resolving changes at follow-up and remained free of tuberculosis disease after 12 months. A positive baseline Actiphage test was associated with the presence of features of incipient tuberculosis requiring treatment (p=0·018). INTERPRETATION: Microbiological and inflammatory features of incipient tuberculosis can be visualised on PET-CT and are associated with M tuberculosis detection in the blood, supporting the development of pathogen-directed blood biomarkers of tuberculosis risk. FUNDING: MRC Confidence in Concept.

CT in the detection of latent tuberculosis: a systematic review.

AIM: To evaluate the use of computed tomography (CT) and low-dose CT in the detection of latent tuberculosis (TB). MATERIALS AND METHODS: A systematic search of literature in adherence with the PRISMA guidelines was carried out. Quality assessment of the included studies was conducted. RESULTS: The search strategy identified a total of 4,621 studies. Sixteen studies were considered eligible and included in the review. There was high heterogeneity among all studies. CT was identified as much more sensitive for the detection of latent TB in all studies despite chest radiography often being recommended in guidelines to assess patients for latent TB. Low-dose CT showed promising results in four of the studies; however, these results were limited due to small sample sizes. CONCLUSION: CT is much superior to chest radiography consistently identifying additional cases of latent TB. There are limited high-quality publications available using low-dose CT but findings thus far suggest low-dose CT could be used as an alternative to standard-dose CT for the detection of latent TB. It is recommended that a randomised controlled trial investigating low-dose CT should be carried out.

Characterizing the Spectrum of Latent Mycobacterium tuberculosis in the Cynomolgus Macaque Model: Clinical, Immunologic, and Imaging Features of Evolution.

Mycobacterium tuberculosis infection outcomes have been described as active tuberculosis or latent infection but a spectrum of outcomes is now recognized. We used a nonhuman primate model, which recapitulates human infection, to characterize the clinical, microbiologic, and radiographic patterns associated with developing latent M. tuberculosis infection. Four patterns were identified. "Controllers" had normal erythrocyte sedimentation rate (ESR) without M. tuberculosis growth in bronchoalveolar lavage or gastric aspirate (BAL/GA). "Early subclinicals" showed transient ESR elevation and/or M. tuberculosis growth on BAL/GA for 60 days postinfection, "mid subclinicals" were positive for 90 days, and "late subclinicals" were positive intermittently, despite the absence of clinical disease. Variability was noted regarding granuloma formation, lung/lymph node metabolic activity, lung/lymph node bacterial burden, gross pathology, and extrapulmonary disease. Like human M. tuberculosis infection, this highlights the heterogeneity associated with the establishment of latent infection, underscoring the need to understand the clinical spectrum and risk factors associated with severe disease.

Expanding Latent Tuberculosis Infection Testing and Treatment in Massachusetts Primary Care Clinics via the ECHO Model.

INTRODUCTION/OBJECTIVES: In the US, reactivation of latent tuberculosis infection (LTBI) accounts for 80% of new cases. In 2016, the US Preventive Services Task Force provided a new recommendation that primary care providers (PCPs) should conduct LTBI screening, whereas in the past, LTBI cases were evaluated and treated by specialty providers. This shift in care revealed knowledge gaps surrounding LTBI treatment among PCPs. This study assessed changes in PCPs' confidence for performing key aspects of LTBI care before and after participation in an LTBI Extension for Community Healthcare Outcomes (ECHO) course. METHODS: The ECHO Model™ is an evidence-based telementoring intervention. Participants were primary care team members from clinics throughout Massachusetts who voluntarily enrolled in the ECHO course. In this mixed-methods evaluation, primary outcomes were PCP self-reported confidence changes by pre- and post-course surveys and post-course semi-structured interviews. RESULTS: Twenty PCPs (43% of registered PCPs) attended at least 3 of the 6 sessions and 24 PCPs (31% of registered PCPs) completed at least one survey. Confidence increased in selecting a test (P = .004), interpreting tuberculosis infection test results (P = .03), and selecting a treatment regimen (P = .004). Qualitative interviews with 3 PCPs revealed practice changes including switching to interferon gamma release assays for testing and using rifampin for treatment. CONCLUSIONS: Use of the ECHO model to train PCPs in LTBI management is feasible and efficacious. For continuing medical education, ECHO courses can be leveraged to reduce health disparities in settings where PCPs' lack of familiarity about a treatment topic contributes to poor health outcomes.

Differentiating between active and latent tuberculosis with chest computed tomography.

PURPOSE: The purpose of this study was to evaluate the capabilities of chest computed tomography (CT) in distinguishing between active and latent tuberculosis in patients positive for interferon-gamma release assay (IGRA) testing, and to compare the performance of CT with that of quantitative IGRA testing in a low incidence setting. MATERIALS AND METHODS: Patients with latent or active tuberculosis define by an IGRA positive test were retrospectively recruited. Sensitivity, specificity and accuracy were determined for CT variables and quantitative IGRA results. Final diagnosis of active tuberculosis was based on clinical data and microbiological culture. Univariable and multivariable analyses were performed using logistic regression model to identify CT variables associated with the diagnosis of active tuberculosis. RESULTS: A total of 92 patients with positive IGRA results who underwent CT examination were included. There were 54 men and 38 women with a mean age of 53.5±18 (SD) years (range: 40-68 years). Of them, 22 patients (24%) had positive Mycobacterium tuberculosis culture and 70 (76%) had latent tuberculosis. Among CT variables, consolidation had the greatest sensitivity (77%; 95%CI: 60-95%) and "tree-in-bud" the greatest specificity (97%; 95% CI: 93-100%) for the diagnosis of active tuberculosis. At univariable analysis "tree-in-bud", splenic calcification and non-calcified lung nodules were the significant variables independently associated with active tuberculosis. At multivariable analysis, the adjusted odds ratio of "tree-in-bud" was 42.91 (95% CI: 5.62-327.42). Using an optimal threshold of 51 spots, quantitative IGRA yielded 64% sensitivity (95% CI: 44-84%) and 61% specificity (95% CI: 50-73%) for the diagnosis of active tuberculosis. CONCLUSIONS: In a low incidence setting, chest CT, especially when "tree-in-bud" pattern is present, is superior to quantitative IGRA testing to identify patients with active tuberculosis among those with positive IGRA testing.

High yield from repeated testing for tuberculosis among high-risk citizens in Denmark.

BACKGROUND: Screening for TB (tuberculosis) among socially marginalized citizens has been implemented in many urban areas in countries with a low incidence of TB, including Denmark. This study aims to describe the findings of the screening programs for TB and latent tuberculosis (LTBI) used in the western part of Denmark in the period 2014-2019. METHODS: Data was collected retrospectively on test results from interferon-gamma release assays (IGRA), spot sputum tests and chest X-rays performed as part of TB and LTBI screening among 1024 socially marginalized citizens in urban areas of western Denmark in 2014-2019. RESULTS: The overall TB incidence was 2148/100.000 and number needed to screen to find one TB case was 39. The incidence of LTBI in the group screened using IGRA was 17.500/100.000. TB incidence when using spot sputum test was 2.5, while TB incidence when using IGRA as the primary screening test was 2.7. In total, 38.9% of TB diagnoses were obtained after the second or third round of screening. CONCLUSION: We demonstrated a high incidence of TB and LTBI among socially marginalized citizens in Denmark. Screening with spot sputum testing and IGRA generated comparable results in diagnosing TB in this setting.

Screening program for latent tuberculosis infection in asylum seekers - a single center experience in Pavia, Italy.

BACKGROUND: The management of Latent Tuberculosis Infection is crucial in fighting Tuberculosis worldwide, and particularly in low incidence European Countries. While guidelines for the management of Tuberculosis in newly arrived immigrants have been issued by the European Center for Disease Control and Prevention and by the National Health Authorities in Italy, these are not widely implemented yet at local level. STUDY DESIGN: We report our program for the screening of Latent Tuberculosis Infection and active Tuberculosis in asylum seekers, jointly implemented by Public Health Authorities and the Infectious Diseases Department of a tertiary care, teaching hospital in Northern Italy. METHODS: We reviewed records of the asylum seekers who were screened at our center via Tuberculin Skin Test and/or Interferon Gamma Release Assay plus chest X-ray and either treated with Isoniazid Preventive Treatment or for active Tuberculosis Disease in case of positive results. RESULTS: We screened 726 migrants, mostly males (97.3%) and from Sub-Saharan Africa (82.2%) and found a high adherence rate for both screening (98.2%) and Isoniazid Preventive Treatment (90.1%). In addition, we found seven cases of active Tuberculosis. CONCLUSIONS: Latent Tuberculosis Infection screening and treatment proved feasible in our program, which should be systematically implemented in asylum seekers reaching Europe.

Chest roentgenography is complementary to interferon-gamma release assay in latent tuberculosis infection screening of rheumatic patients.

BACKGROUND: A study of latent tuberculosis infection (LTBI) burden by chest roentgenography (CXR) with reference to interferon-gamma release assay (IGRA) is still lacking in rheumatic patients of an intermediate tuberculosis burden area. METHODS: We retrospectively reviewed clinical data of patients with rheumatoid arthritis (RA), ankylosing spondylitis (AS), or psoriatic arthritis (PsA) receiving LTBI screening for biologics from Jan 2013 to April 2014. RESULTS: A total of 238 rheumatic patients who underwent LTBI screening were included in this study, of whom 46 (19.3%) had positive IGRA tests, 178 (74.8%) had negative results, and 14 (5.9%) had indeterminate results. Radiological findings suggesting healed tuberculosis (CXR-old-TB) were found in 18.1% of all patients, 23.9% in the IGRA -positive patients vs 16.9% in the IGRA-negative patients (OR 1.55 95% CI: 0.71-3.39, p = 0.27). Forty (40/46, 87.0%) IGRA-positive patients received isoniazid prophylaxis and 77.5% of them finished treatment. Six patients developed adverse effects of isoniazid treatment, resulting in an overall number needed to harm (NNH) of 6.7 (40/6). IGRA-non-positive patients with old TB-suggestive CXR comprised 13.4% (32/238) of all our rheumatic patients, and one of them developed pulmonary tuberculosis within one year after screening. CONCLUSIONS: LTBI disease burden in rheumatic patients is substantial according to the estimation of CXR and IGRA screening. Correlation between CXR and IGRA is not significant in rheumatic patients, which implies their complementary roles. IGRA-non-positive patients with old TB-suggestive CXR comprise a significant portion in rheumatic patients and merit cautious follow-up by rheumatologists, tuberculosis specialists, and pulmonologists.

Towards more accurate 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) imaging in active and latent tuberculosis.

Tuberculosis (TB) is one of the leading causes of death worldwide. Although the disease is curable and preventable, it is underdiagnosed in many parts of the world. Positron emission tomography (PET) imaging using 18 F-FDG in TB can localise disease sites and the extent of disease. 18F-FDG accumulates in the immune cells that participate in inflammation and granuloma formation, such as activated macrophages and lymphocytes. Therefore, FDG PET/CT scanning is now being evaluated for its usefulness in the diagnosis of extrapulmonary TB and in monitoring the response to treatment. FDG PET/CT imaging is positive and has high sensitivity in active TB, complementing conventional radiological imaging (X-ray, computed tomography, magnetic resonance imaging) in the diagnosis of primary pulmonary, extrapulmonary, and post-primary or miliary TB. FDG PET/CT has low specificity when it is used for solitary pulmonary nodule characterization, and its ability to differentiate TB from malignancy is limited in this setting. Dual point imaging has been proposed as a way to overcome this limitation. FDG PET/CT can reliably differentiate active from inactive disease, and there is promising evidence that it can contribute to the assessment of the response to treatment with an impact on patient management. FDG PET/CT has been found positive in cases of latent TB infection and its ability to identify activation early is currently being explored. More studies are needed to establish the utility of this method in recognizing multidrug-resistant TB cases. Furthermore, other PET radiotracers might prove useful in the functional imaging of TB infection in the future.

Contribution to differential diagnosis of sarcoidosis and disseminated tuberculosis.

A previously healthy 54-year-old ethnically Danish man was referred to the Department of Infectious Diseases at Aarhus University Hospital after an unexpected detection of Mycobacterium tuberculosis DNA in his lungs. Further examination revealed widespread dissemination of the tuberculosis (TB) to brain, mastoid, urinary and gastrointestinal tract. Thirteen months earlier, the patient was orchiectomised due to recurring inflammation of the right testicle. Three and a half months prior to admission to our department the patient started immunosuppressive therapy with steroids due to radiological and histological findings in the lungs that were interpreted as sarcoidosis (SA). This treatment is likely to be co-responsible for the pronounced dissemination of the TB. The patient was Bacillus Calmette-Guérin (BCG)-vaccinated as a child and had no apparent risk factors for TB apart from travelling in TB-endemic countries until 10 years before falling ill. Screening for latent TB was not performed prior to starting steroid treatment.

Is there a fundamental flaw in Canada's post-arrival immigrant surveillance system for tuberculosis?

BACKGROUND: New immigrants to Canada with a history of tuberculosis or evidence of old healed tuberculosis on chest radiograph are referred to public health authorities for medical surveillance. This ostensible public health protection measure identifies a subgroup of patients (referrals) who are at very low risk (compared to non-referrals) of transmission. METHODS: To assess whether earlier diagnosis or a different phenotypic expression of disease explains this difference, we systematically reconstructed the immigration and transmission histories from a well-defined cohort of recently-arrived referral and non-referral pulmonary tuberculosis cases in Canada. Incident case chest radiographs in all cases and sequential past radiographs in referrals were re-read by three experts. Change in disease severity from pre-immigration radiograph to incident radiograph was the primary, and transmission of tuberculosis, the secondary, outcome. RESULTS: There were 174 cohort cases; 61 (35.1%) referrals and 113 (64.9%) non-referrals. Compared to non-referrals, referrals were less likely to be symptomatic (26% vs. 80%), smear-positive (15% vs. 50%), or to have cavitation (0% vs. 35%) or extensive disease (15% vs. 59%) on chest radiograph. After adjustment for referral status, time between films, country-of-birth, age and co-morbidities, referrals were less likely to have substantial changes on chest radiograph; OR 0.058 (95% CI 0.018-0.199). All secondary cases and 82% of tuberculin skin test conversions occurred in contacts of non-referrals. CONCLUSIONS: Phenotypically different disease, and not earlier diagnosis, explains the difference in transmission risk between referrals and non-referrals. Screening, and treating high-risk non-referrals for latent tuberculosis is necessary to eliminate tuberculosis in Canada.

Reactivation of intraabdominal tuberculous lymphadenopathy after drug-eluting beads transcatheter arterial chemoembolization in a patient with hepatocellular carcinoma.

Owing to effective treatments and sanitary improvements, the incidence of latent tuberculosis infection (LTBI) has decreased. However, approximately one-quarter of the world's population is thought to have LTBI, and the reactivation of tuberculosis (TB) sometimes occurs in immunocompromised hosts. A 54-year-old man presented with a fever. The patient had past histories of alcoholic and hepatitis C virus-related cirrhosis and hepatocellular carcinoma (HCC). He was treated with drug-eluting beads transarterial chemoembolization (DEB-TACE) for HCC three times, beginning 10 months before his current visit. A computed tomography scan showed enlarged intraabdominal lymph nodes with calcification, and the interferon-gamma release assay for TB infection was positive. The patient was diagnosed with tuberculous reactivation. Anti-TB therapy was administered to the patient, after which we restarted TACE and the TB infection remains controlled. In this case, we presumed that DEB-TACE is associated with the reactivation of TB infection and that anthracycline increases the risk of reactivating TB infection. In summary, we experienced a case of TB reactivation during the clinical course of a patient with HCC who was treated with DEB-TACE. When patients with HCC are treated with TACE, their symptoms, laboratory data, and imaging results should be monitored when latent TB infections are suspected.

The usefulness of routine chest radiograph examinations in patients treated with TNF inhibitors for inflammatory arthritis in South Korea.

OBJECTIVES: We aimed to investigate the usefulness of routine chest radiograph (CXR) examinations for patients with inflammatory arthritis treated with a tumor necrosis factor (TNF) inhibitor in terms of (i) the role of CXR in baseline latent tuberculosis infection (LTBI) screening and (ii) detecting asymptomatic active tuberculosis after TNF inhibitor initiation. METHODS: From January 2011 to June 2017, 469 patients with inflammatory arthritis were enrolled in the study at a tertiary referral center in South Korea. At our institution, CXR was performed for all patients undergoing a tuberculin skin test (TST) and/or an interferon-gamma release assay (IGRA) at the LTBI screening visit. LTBI treatment was determined by (i) positive TST or IGRA or (ii) CXR findings suggestive of spontaneously healed tuberculosis. After TNF inhibitor initiation, patients were recommended to undergo CXR at a specified interval. RESULTS: Of 469 patients, 187 were treated for LTBI. Among them, 181 patients were treated for LTBI because of a positive TST or IGRA result. TST was considered positive if induration size was ≥10 mm. The remaining six patients were considered positive on the basis of CXR findings compatible with spontaneously healed tuberculosis, such as noncalcified nodules with distinct margins and fibrotic linear opacity, despite demonstrating negative results for TST and IGRA. Thus, CXR had a diagnostic value as a baseline LTBI test in 6 (1.3%) patients. After TNF inhibitor initiation, 2 patients who had respiratory symptoms were diagnosed with active tuberculosis. For asymptomatic patients, routine CXR follow-up could not detect any case of active pulmonary tuberculosis within 1 year (n = 219) or after 1 year (n = 217). CONCLUSIONS: CXR should be performed as one of the LTBI screening tests for patients with inflammatory arthritis in a tuberculosis-prevalent country. However, after TNF inhibitor treatment, routine CXR follow-up was not advantageous.

FDG-PET/CT activity leads to the diagnosis of unsuspected TB: a retrospective study.

OBJECTIVE: Mycobacterium tuberculosis infection leads to latent or active tuberculosis (TB). Increased uptake on 18F-fluoro-2-deoxy-glucose-positron emission tomography/computed tomography (FDG-PET/CT) has been reported in the lungs and lymph nodes of individuals with recent infection and active TB, but not in individuals without known recent exposure or suggestive symptoms. We describe five patients with lung nodules not suspected to be due to TB in whom abnormalities on FDG-PET/CT scans ultimately were attributed to TB infection. RESULTS: Patient records were searched using the words "positron emission tomography/computed tomography" and 24 codes for TB between 2004 and 2013. Patients with a diagnosis of TB and a PET/CT scan were included. Clinical and radiographic data were retrieved. PET/CT images were reviewed by an experienced radiologist. FDG-PET/CT scans revealed elevated FDG-uptake in lungs of five patients subsequently diagnosed with active (n = 3) or clinically inactive (n = 2) tuberculosis. Uptake magnitude was unrelated to disease activity. These findings suggest that tuberculosis latency may include periods of percolating inflammation of uncertain relationship to future disease risk.

The potential of imaging tools as correlates of infection and disease for new TB vaccine development.

The development of an improved vaccine to stimulate an effective response against Mycobacterium tuberculosis (MTB) infection and disease will be a major breakthrough in the fight against TB. A lack of tools to adequately track the progression or resolution of events in TB pathogenesis that occur at bacterial loads below the threshold for culture in human samples seriously hampers vaccine development and evaluation. In this review we discuss recent studies that use new imaging applications, modalities and analysis techniques to provide insight into the dynamic processes of MTB infection and disease that are challenging to monitor. These include early infection, the spectrum of latency and subclinical disease, the paucibacillary state induced by treatment, and events leading to recurrence, including relapse.

Mobile phone-based evaluation of latent tuberculosis infection: Proof of concept for an integrated image capture and analysis system.

BACKGROUND: The tuberculin skin test is the most widely used method for detecting latent tuberculosis infection in adults and active tuberculosis in children. We present the development of a mobile-phone based screening tool for measuring the tuberculin skin test induration. METHOD: The tool makes use of a mobile application developed on the Android platform to capture images of an induration, and photogrammetric reconstruction using Agisoft PhotoScan to reconstruct the induration in 3D, followed by 3D measurement of the induration with the aid of functions from the Python programming language. The system enables capture of images by the person being screened for latent tuberculosis infection. Measurement precision was tested using a 3D printed induration. Real-world use of the tool was simulated by application to a set of mock skin indurations, created by a make-up artist, and the performance of the tool was evaluated. The usability of the application was assessed with the aid of a questionnaire completed by participants. RESULTS: The tool was found to measure the 3D printed induration with greater precision than the current ruler and pen method, as indicated by the lower standard deviation produced (0.3 mm versus 1.1 mm in the literature). There was high correlation between manual and algorithm measurement of mock skin indurations. The height of the skin induration and the definition of its margins were found to influence the accuracy of 3D reconstruction and therefore the measurement error, under simulated real-world conditions. Based on assessment of the user experience in capturing images, a simplified user interface would benefit wide-spread implementation. CONCLUSIONS: The mobile application shows good agreement with direct measurement. It provides an alternative method for measuring tuberculin skin test indurations and may remove the need for an in-person follow-up visit after test administration, thus improving latent tuberculosis infection screening throughput.

Use of a leukocyte-targeted peptide probe as a potential tracer for imaging the tuberculosis granuloma.

Granulomas are the histopathologic hallmark of tuberculosis (TB), both in latency and active disease. Diagnostic and therapeutic strategies that specifically target granulomas have not been developed. Our objective is to develop a probe for imaging relevant immune cell populations infiltrating the granuloma. We report the binding specificity of Cyanine 3 (Cy3)-labeled cFLFLFK-PEG12 to human leukocytes and cellular constituents within a human in vitro granuloma model. We also report use of the probe in in vivo studies using a mouse model of lung granulomatous inflammation. We found that the probe preferentially binds human neutrophils and macrophages in human granuloma structures. Inhibition studies showed that peptide binding to human neutrophils is mediated by the receptor formyl peptide receptor 1 (FPR1). Imaging the distribution of intravenously administered cFLFLFK-PEG12-Cy3 in the mouse model revealed probe accumulation within granulomatous inflammatory responses in the lung. Further characterization revealed that the probe preferentially associated with neutrophils and cells of the monocyte/macrophage lineage. As there is no current clinical diagnostic imaging tool that specifically targets granulomas, the use of this probe in the context of latent and active TB may provide a unique advantage over current clinical imaging probes. We anticipate that utilizing a FPR1-targeted radiopharmaceutical analog of cFLFLFK in preclinical imaging studies may greatly contribute to our understanding of granuloma influx patterns and the biological roles and consequences of FPR1-expressing cells in contributing to disease pathogenesis.