In high-burden HIV and tuberculosis settings, extrapulmonary and disseminated TB can be difficult to recognize quickly. Symptoms may be nonspecific, microbiologic confirmation may be challenging, and access to CT, formal ultrasound, or even reliable chest radiography can be limited.
The Focused Assessment with Sonography for HIV-associated Tuberculosis, or FASH exam, is a focused point-of-care ultrasound protocol designed to help clinicians look for sonographic findings associated with extrapulmonary TB in people living with HIV. The exam can be performed at the bedside and can provide immediate information when other diagnostic resources are limited.
The Direct Answer
FASH is a focused POCUS protocol used primarily in people living with HIV when extrapulmonary or disseminated TB is suspected, especially in high-TB-burden settings. It looks for findings such as pericardial or pleural effusion, ascites, enlarged abdominal lymph nodes, and focal liver or spleen lesions. These findings can support the clinical assessment, but FASH alone does not confirm or exclude tuberculosis.
That final point is important. FASH is valuable because it can rapidly change the clinician’s level of suspicion and help guide the next step. Its findings must still be interpreted alongside the patient’s symptoms, epidemiology, laboratory testing, microbiology, other imaging when available, and local TB treatment algorithms.
What Is the FASH Exam?
FASH was developed for settings where HIV-associated extrapulmonary TB is common and access to diagnostic imaging is limited. The original protocol borrowed the idea of a short, repeatable bedside examination from other focused ultrasound protocols and applied it to findings commonly seen in HIV/TB co-infection. [1]
The exam is not a comprehensive abdominal, cardiac, or thoracic ultrasound. It is designed around a small number of targeted questions that can be answered rapidly by a clinician trained to recognize the relevant patterns.
That makes FASH particularly suited to settings where the alternative may be delayed imaging, long referral distances, limited laboratory capacity, or no advanced imaging at all.
What Does FASH Look For?
| FASH Target | What the Clinician Is Looking For | Why It May Matter |
|---|---|---|
| Pericardium | Pericardial effusion | Can occur with TB pericarditis, but other causes must be considered. |
| Pleural spaces | Pleural effusion | May accompany pleural TB or other infectious, cardiac, malignant, or inflammatory disease. |
| Peritoneal cavity | Ascites / free fluid | Can be seen with abdominal TB but is nonspecific. |
| Abdominal lymph nodes | Enlarged periportal, para-aortic, or other abdominal nodes | May raise suspicion for abdominal or disseminated TB; lymphoma and other infections are important alternatives. |
| Spleen | Small hypoechoic focal lesions | Can be associated with disseminated TB but are not unique to TB. |
| Liver | Focal hypoechoic lesions / microabscess-like findings | May support concern for disseminated infection but have a broad differential diagnosis. |
FASH Basic and Expanded Findings
The original FASH publication described a basic examination focused on pericardial effusion, pleural effusion, and ascites. As clinicians gain experience, the exam can be extended to look for abdominal lymphadenopathy and focal liver or splenic lesions. [1]
Some contemporary teaching resources also combine FASH with other lung-ultrasound findings when clinically useful. The exact protocol should follow the clinician’s training program and local standard rather than expanding ad hoc at the bedside.
How Should a FASH Exam Be Interpreted?
The safest way to understand FASH is as a probability-changing examination. A finding can make extrapulmonary or disseminated TB more plausible in the right patient, but the same finding may have other causes.
A 2024 review and meta-analysis found that two of the most studied abdominal findings had relatively low sensitivity but higher specificity. Enlarged abdominal lymph nodes had an estimated sensitivity of 39% and specificity of 89%, while hypoechoic splenic lesions had an estimated sensitivity of 30% and specificity of 93%. [2]
A separate prospective study of 414 HIV-positive adults with suspected TB found that the overall FASH protocol had 71% sensitivity and 57% specificity against microbiologic confirmation. [3]
What These Numbers Mean
Published diagnostic performance varies by population, protocol, operator, and reference standard. FASH should not be treated as a standalone ‘positive/negative TB test.’ A negative exam can miss disease, and a positive feature may reflect another infection, malignancy, or non-TB condition.
FASH Findings Are Not Specific to Tuberculosis
The 2024 review highlighted several important alternative diagnoses for FASH target findings in people living with HIV, including nontuberculous mycobacterial infection, invasive fungal disease, visceral leishmaniasis, lymphoma, Kaposi sarcoma, and other opportunistic or systemic diseases. [2]
When available and clinically appropriate, ultrasound can also help identify a safe site for diagnostic sampling. The scan should therefore be connected to a broader diagnostic plan rather than used as an endpoint.
A Negative FASH Does Not Exclude TB
This is the other side of the same limitation. Low sensitivity for several individual features means that a normal or technically limited FASH exam cannot safely rule out extrapulmonary TB when clinical suspicion remains high.
If the patient’s presentation remains concerning, clinicians should continue the diagnostic pathway using locally available microbiologic testing, laboratory studies, chest imaging, comprehensive ultrasound, CT or MRI, sampling, specialist input, or empiric treatment pathways according to local guidance.
Why FASH Matters in HIV/TB Care
The value of FASH becomes clearest when the diagnostic alternatives are scarce. In well-resourced systems, point-of-care ultrasound may save time before formal imaging. In resource-constrained systems, it may be the only imaging available during the encounter.
That distinction shaped a 2025 qualitative project led by Marcela Osorio, MS4, in collaboration with GUSI. Four frontline clinicians in Lesotho, Zambia, and Malawi described how they used FASH after completing GUSI training. Most practiced in family medicine or similar generalist roles in semi-rural settings, and three had not received prior FASH training.
Their experiences do not establish diagnostic accuracy – the sample was small and qualitative – but they show what implementation looks like where HIV/TB co-infection is part of routine clinical care.
What Frontline Providers Told GUSI
Faster Access to Actionable Information
Providers described cases in which advanced imaging was unavailable, unaffordable, or too slow to help with the immediate decision. In that context, having an ultrasound at the bedside gave them another source of information while they were still responsible for the patient.
Several felt that FASH shortened the path to a working diagnosis and treatment plan, particularly when other investigations were delayed or inconclusive. This does not mean treatment should be based on FASH alone. It shows why rapid bedside information matters when the conventional diagnostic pathway is fragile.
More Confidence When Other Testing Is Limited
Participants also described FASH as increasing their confidence when they were already concerned about disseminated or extrapulmonary TB but did not have a definitive result from other tests.
The clinically responsible interpretation is not that ultrasound ‘proves’ TB. Instead, a compatible FASH finding can become one additional piece of evidence in a patient whose epidemiology and clinical picture already create meaningful pretest probability.
A Protocol That Is Teachable, but Skill Still Requires Repetition
One provider described FASH as “simple to follow and easy to teach.” That simplicity is one of the protocol’s strengths, but the interviews also made clear that competence does not come from watching a module once.
Clinicians reported difficulty maintaining probe skills when they did not have consistent access to ultrasound devices. They specifically mentioned image depth, gain, probe positioning, and confidence in recognizing pathology as skills that deteriorate without practice.
The Biggest Barriers to FASH Implementation
Devices and Basic Consumables
The most obvious barrier was not educational content. It was access. Participants described sharing only a few handheld ultrasound devices across programs or hospitals. In some cases, the machine existed but could not be used when basic supplies such as ultrasound gel were unavailable.
That matters twice: limited equipment restricts patient access and also restricts the clinician’s opportunity to practice enough to become proficient.
Training, Acceptance, and Image Quality
Participants described uneven familiarity with FASH among colleagues and supervisors. Some clinicians remained more comfortable waiting for a formal radiology examination even when the bedside operator had completed training.
That skepticism is not solved by enthusiasm alone. Programs need a way to show image quality, document findings, review mistakes, and demonstrate that clinicians are scanning within a defined scope.
Longitudinal Mentorship and Quality Assurance
The strongest implementation theme in the interviews was the need for ongoing feedback. Providers wanted a way to review scans with more experienced colleagues, discuss difficult cases, and learn from image-quality and interpretation errors.
That is a broader POCUS lesson: a course starts the learning process, but longitudinal mentorship, scan review, image archiving, and quality assurance are what turn a new skill into a sustainable clinical service.
Where FASH Fits in the TB Diagnostic Pathway
| FASH Can Help With | FASH Cannot Do Alone |
|---|---|
| Rapidly identify ultrasound findings associated with EPTB | Confirm Mycobacterium tuberculosis infection |
| Increase or decrease clinical suspicion in the right epidemiologic context | Rule out EPTB after a negative or technically limited exam |
| Identify effusions, ascites, lymph nodes, or focal organ lesions | Determine that every abnormality is caused by TB |
| Help prioritize further testing, referral, sampling, or treatment decisions | Replace microbiologic testing, comprehensive imaging, or specialist evaluation when available and needed |
| Support bedside reassessment in settings with limited imaging access | Compensate for inadequate training, poor image quality, or lack of clinical context |
The exact next step depends on the patient and the health system. FASH works best inside a locally defined HIV/TB diagnostic algorithm that specifies what to do with positive, negative, limited, and unexpected findings.
Training FASH Safely
FASH was designed to be learnable by clinicians without extensive prior ultrasound experience, but basic ultrasound skills still matter. Training should include:
- Ultrasound physics, probe orientation, depth, gain, and image optimization
- Normal anatomy at every FASH window
- Recognition of effusions, ascites, lymph nodes, and focal organ lesions
- Common mimics and differential diagnoses
- How to document and archive representative images
- When the exam is technically limited or nondiagnostic
- How FASH findings fit into local TB testing and treatment pathways
- Supervised scanning, image review, and ongoing mentorship
The 2024 evidence review specifically recommends basic ultrasound training, including the FASH protocol and ultrasound-guided diagnostic interventions, for providers caring for people living with HIV in resource-limited settings. [2]
GUSI’s Role in FASH Education and Global Health
The frontline interviews reinforce that training has to be paired with access and support. GUSI currently includes FASH content within its POCUS education ecosystem and offers several ways to continue learning:
| GUSI Resource | Role in FASH / POCUS Development |
|---|---|
| POCUS Essentials Course | Foundational online education, including FASH-related learning content. |
| POCUS Essentials Virtual Fellowship | Longitudinal scanning, mentoring, and a pathway that includes FASH scan types. |
| FASH Fellowship | A dedicated, longitudinal fellowship track for clinicians building FASH competency — supervised scanning, case review, and mentorship focused specifically on HIV-associated TB ultrasound. |
| Ultrasound Scan Reviews | Human feedback on image acquisition and interpretation. |
| Global Health Initiatives | Programs that combine training, equipment access, mentorship, and local partnerships. |
| In-Person Workshops | Hands-on practice for programs that need practical skill development. |
From Training to Sustainable Practice
GUSI has just launched a dedicated FASH Fellowship for clinicians who want structured, longitudinal training in this exact protocol — supervised scans, case-based mentorship, and image review built around HIV-associated TB findings. If your team is building FASH capacity, this is the fastest path from course completion to independent competence.
