Thread by @FilaMentor

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First of 2 tweets! #GalactoMagic

75F w/ lupus, HTN, recent diagnosis of HIV (viral load 30,000, CD4- 57), presents to ED in winter w/ 4 weeks of shortness of breath & cough. T 38.5C, HR 105, BP 105/80, RR 20, O2 94% on 3L. Exam is notable for crackles & rhonchi in both lungs

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Labs: WBC 2,600, Hb 7.5 g/dL, platelet 70,000. CXR shows diffuse opacities. You have suspicion for Pneumocystis jirovecii pneumonia

Which of the following is the best non-invasive test to order to help confirm the diagnosis?

1/11
Answer: Serum BDG

⭐️LDH elevation is nonspecific and can be elevated in many diffuse pulm processes

Serum GM is not helpful in diagnosing PJP since its cell wall does not contain GM

BDG is a cell wall polysaccharide present in many pathogenic fungi including P. jirovecii

2/
With serum Pneumocystis PCR- earlier studies didn’t detect PJP

More recent studies have shown high sens & NPV for PJP in HIV-infected pts, but the serum PCR suffers from poor specificity

💥Because of these differences, serum PCR is not recommended

pubmed.ncbi.nlm.nih.gov/32400869/

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PJP was initially described in malnourished children in early 1900s, then identified as an OI in patients with T cell defects

Pneumocystis causes pneumonia in a broad range of hosts

⚡️Risk factors for PJP are noted in the table below

4/
PJP presents w/ dyspnea, hypoxia, fever

Difference in presentation b/w HIV & non-HIV is time, along w/ diff in tests (stain sensitivity is higher in HIV)

In HIV, time course is subacute (weeks), whereas in non-HIV, time course is shorter (days-week)

pubmed.ncbi.nlm.nih.gov/32000290/

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PJP diagnostics from resp tract is complex!

🍏Definitive diag is made by seeing organisms in lung tissue/secretions

🍎Induced sputum w/ direct immunofluorescent staining is used, but a negative smear cannot exclude PJP

Bronch w/ BAL is helpful, esp if induced sputum is neg

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🎾Using blood samples has the advantage of being easily obtained

🥎Now, we will talk about using serum BDG to diagnose PJP in AIDS patients

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This study looked at BDG test characteristics in AIDS pts w/ RESPIRATORY symptoms (compared to BDG study looking at all comers-pubmed.ncbi.nlm.nih.gov/21690628/)

Using BDG 80, BDG had sens 93%, spec 75%, PPV 96%, NPV 60%

Median BDG was 405; w/o PJP it was 41

pubmed.ncbi.nlm.nih.gov/23698062/

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As you can see from the numbers above, it can help support a diagnosis of PJP in AIDS patients

But just like w/ any test, it is not perfect

🌈The authors proposed the algorithm below for using BDG as a tool to diagnose PJP in AIDS patients

pubmed.ncbi.nlm.nih.gov/23698062/

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A limitation of BDG is its non-specificity

Pts w/ AIDS can have:
🌑other infections w/ +BDG (candida)
🌑multiple infections simultaneously that cause +BDG (Histo + Pneumocystis)
🌑+BDG not from a fungus (albumin)

As a refresher, please review this table by @febrilepodcast

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BDG is helpful to diagnose PJP in AIDS pts

💫There are studies that suggest BDG for PJP is not as sens when used in other immunocompromised states, maybe 2/2 lower fungal burden

For a point-counterpoint discussion of BDG for PJP, see the review here

pubmed.ncbi.nlm.nih.gov/31434728/

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Finally, to wrap everything up, @rabihmgeha and @RexHLee put together this excellent illness script for PJP in both HIV and non-HIV patients @CPSolvers