Here are some of the highest-yield pearls related to the clinical presentation and diagnosis of community-acquired pneumonia (CAP)!
Let me know what your favorite pearls are, and if you'd add anything!
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You can still have a viral infection AND a bacterial pneumonia; having a positive RVP does not mean you should withhold antibiotics in the right clinical scenario!
CURB-65 and PSI are used to calculate mortality risk and have technically not been validated for determining the ideal place of care.
They can be valuable for helping you determine sick vs not sick, but in the end your clinical gut trumps all.
Rhinorrhea and sore throat are more commonly seen in URI and are less typical for CAP.
Sputum samples are usually not sent due to low sensitivity/yield.
Strep pneumo and H Flu are tough to grow in culture.
It is considered adequate if there are >25 PMNs and <10 squamous epithelial cells.
Otherwise, there is concern that the sample is saliva.
Note that this is NOT the same for tracheal aspirates in intubated ICU patients which can be VERY helpful for diagnosing a healthcare-associated pneumonia and identifying the bug and resistance patterns.
Only send blood cultures if there is concern for severe pneumonia or sepsis; they are positive in <20% of inpatients with PNA.
MRSA Nasal Swab has a 98% NPV for MRSA pneumonia.
Thus, in most cases, if it's negative, you can feel comfortable pulling off MRSA coverage
Note that this was only studied on the admission MRSA swab, not if the patient developed concern for HAP after being admitted.
Procalcitonin was validated in ICU settings to try and limit the duration of antibiotics. Thus, a procal on admission can be tough to interpret.
You can consider stopping abx if the level trends down to <80% of peak or is <0.25-0.50; note that it has variable sensitivity
If a patient's procalcitonin level is less than 0.5, it might be okay to stop giving them beta-lactam antibiotics but keep giving them azithromycin or doxycycline.
This is because gram negatives raise procalcitonin, whereas atypicals are less likely to raise it.
Legionella Urine Antigen should be sent in severe CAP, or there is concomitant hyponatremia, diarrhea, or recent exposure.
Note that the classic teaching of hyponatremia associated with legionella is likely overstated and not sensitive.
Bacterial pneumonia shouldn't cause pulmonary nodules. If present, it would be more consistent with a fungal infection in the right patient.
Beta-D-glucan (BDG) is sensitive but not specific for fungal infection.