Detection of a bacterial infection: Procalcitonin test

[MikeOr]

How to figure out if antibiotics should be considered ? There is a blood test measuring levels of Procalcitonin: if it is below 0.1 ng/mL, a bacterial infection is very unlikely, so antibiotics would be of no help.

My question is: how reliable is this indicator, especially on the false negative side ? Have anybody had a case when level of Procalcitonin was low, but in the end it still turned out to be a bacterial infection ?

[CaptRon1976]

My personal knowledge is limited. In 2019 I was admitted to hospital with sepsis , coma and encephalopathy from pneumonia. I was treated with IV antibiotics for what turned out to be pneumococcal pneumonia. After waking from coma the doctors used the low procalcitonin test as the major criteria for stopping treatment and discharged me the next day.

[MikeOr in reply to CaptRon1976]

Thanks CaptRon1976. Did they have another procalcitonin test before they started the treatment, to compare ?

[CaptRon1976 in reply to MikeOr]

to my knowledge no. I hit ER in coma and they wasted no time starting IV abx.

[SofiaDeo]

It hasn't been tested in those with significant immune deficiencies. False positives as well as false negatives can occur. Here's the protocol my Alma Mater uses:

med.umich.edu/asp/pdf/adult...