Thread by @FilaMentor

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First of 2 tweets! #GalactoMagic

80F nursing home resident presents w/ 3 days of fever, cough, & SOB

Vitals: T 38.6C, HR 110, BP 120/80, O2 94% on 3L. Exam notable for left basilar rhonchi & crackles

CXR shows LLL opacity. She is started on ceftriaxone & doxy

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2 days later, she is still having intermittent fevers with Tmax 38.1C, O2 94% on 3L, RR 30

A CT chest reveals a dense LLL consolidation

In addition to sputum cultures, which of the following tests should be ordered?

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Answer: Blood cultures

The patient is a nursing home resident w/ ongoing fevers, hypoxia, high RR, with a LLL consolidation

In addition to sputum cx, the patient should also have blood cx (fits pneumonia severity index IV)

There is no dysuria to prompt an UA

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. @ValeriaFabreMD, @sanjayvdesai and others published a review on indications for blood cultures in non-neutropenic patients

The figure below is full of rich information, but basically comes down to the pre-test probability of bacteremia

pubmed.ncbi.nlm.nih.gov/31942949/

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The ATS/IDSA guidelines also discuss when to order sputum and blood cultures

atsjournals.org/doi/pdf/10.116…

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With respect to the consolidation, the patient could still have a dense bacterial PNA

The patient has no PMHx and does not have any known risk factors for IFI. Your pre-test probability for a fungal infection is low

As such, there is no indication to order serum BDG or GM

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🌞Fungi can cause infections depending on epi & host factors

🌞Given challenges of culture-based diagnostics, serum biomarkers such as BDG & GM can aid in the diagnosis

🌞Performance of these biomarkers depend on organism, host factors & prevalence

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No diagnostic test is perfect. In order to use tests to our advantage, we need to know disease prevalence to calculate PPV & NPV

⚡️The disease prevalence, as well as clinical presentation, drives pre-test probability, which influences post-test likelihood of disease

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To help determine pre-test probability, you can use this table with risk factors for fungal infections & patient characteristics

⭐️Your pre-test probability for fungal infections increases as you add more risk factors

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Once you get a feel for pre-test probability (probability of disease based on prevalence according to host risks & clinical presentation) of the fungal infection for your pt, you can see how this value impacts the post-test probabilities of BDG & GM

https://twitter.com/FilaMentor/status/1357745269799067655?s=20

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As a review, both BDG & GM are polysaccharide cell wall components of fungi

This Venn diagram shows the BDG/GM status of fungi

Mucorales is off the diagram

Crypto & Blasto are on the border for BDG since they can sometimes cause a low level BDG

pubmed.ncbi.nlm.nih.gov/29125373/

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Now you’re thinking, it'd be nice to review that chart again about BDG/GM: which pathogens test positive w/ the markers, sens/spec, & causes of false positive (which are true positives but not detecting fungus)

@swinndong w/ @febrilepodcast made that amazing infographic!

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It’s important to know:
💫pre-test probability of a fungal infection (knowing pt characteristics & presentation)
💫prevalence of IFI in specific patient populations
💫test characteristics of biomarkers

...before ordering serum fungal markers

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Just this month, the EORTC/MSGERC reviewed the revised IFI definition guidelines. 2 of the articles pertained to BDG & GM (links below)

This amazing table proposes recommendations for BDG testing

pubmed.ncbi.nlm.nih.gov/33709130/

pubmed.ncbi.nlm.nih.gov/33709125/

Thank you so much for tuning in for another tweetorial on a beautiful #FungalFriday