05/01/2026
Clinical evidence for the three emergencies in suspicion of severe infections: CRP, Procalcitonin and Lactate
In cases of severe fever, deterioration of consciousness, a drop of pressure, or shortness of breath with suspicion of infection,
There are 3 analyses, if you fear correctly, they will shorten your path:
Is it really a bacterial infection? Is the body in for shock? Is the situation getting worse or not responding?
The idea is not that every analysis is a diagnostic, the idea is that each of them measures a different angle of the same problem.
First up: CRP
Description: Liver protein rises with inflammation in general.
Clinical indication: Sensitive to inflammatory but abnormal It means higher in bacteria, viruses, and non communicable infections.
Important point: CRP is relatively late, rises after hours and peaks late, which is excellent to follow but not always the best indicator at the first moment.
Second: Procalcitonin
Description: An indicator that tends to rise with systemic bacterial infection more than others.
Clinical Indication: Helps to reverse bacterial inflammation, especially if the clinical image is unclear, and is also very helpful in tracking antibiotics response and reducing overuse.
Important point: not an “opposite button.” So, treatment does not prevent even if the patient has a shock, and the virus does not prove 100% if it is low.
Third: Lactate
Description: An indirect indicator of low blood pressure and oxygen deficiency at the tissues of the tissue level, or impairment of oxygen use during shock.
Clinical indication: this is not an "infection" analysis, this is a "shock" analysis. It can rise high before the pressure falls, which makes its value dangerous and important.
The false experience that ruins the decision:
1. High CRP remains bacteria. Wrong.
2. Low procalcitonin so that there is no bacteria. Not all the time.
3. High lactate must be low blood pressure. Wrong, sometimes the lactates increase and the pressure is still normal.
How do you practically read them?
If the Lactate is high:
Lactate is greater or equal to 2: An indicator that there is stress on the tract or onset of shock, the patient should be re-evaluated quickly, look for the source of the infection, and follow up the vital signs and urine.
Lactate greater or equal 4: High-risk alert, treat as a shock until proven otherwise. This calls for resuscitation of fluids by case, implanted pre-contraceptives if effective without delay, an early antibiotics, adhesive monitoring and lactate re-measuring to follow improvement. The important thing is not only the number, the important thing is whether it goes down, steady or up.
If Procalcitonin is high: numbers vary by protocol, but common reading:
Less than 0.1: low probability of systemic bacterial infection.
0.1 to 0.25: less likely, but final decision is clinical.
Larger from 0.25 to 0.5: probability of an infected bacterium, especially if symptoms are severe.
Larger than 0.5: Supports the presence of systemic bacterial infection or severe inflammation.
Larger than 2: Sepsis is clearly raised, especially if accompanied by signs of shock or organ failure. IMPORTANT ALERT: Kidney failure and some severe inflammatory cases can raise procalcetonin, do not read separately from the picture.
If the CRP is high:
A slight to moderate increase in possible viral infection or non-bacterial inflammation.
Large elevations (like tens to hundreds) support severe inflammation but does not prove the type of microbes. His gold value is following: If CRP and it goes down with treatment, this is a sign of general response even if the cause is not just bacteria.
Connecting them is what tells you what to do:
High procalcitonin with high CRP: Supports strong bacterial inflammation, especially if systemic symptoms are present.
Lactate is high with any of them: Here you are dealing with shock risk and deficiency, priority CPR, early contraception, and organ monitoring.
High CRP with Low Procalcitonin: Think of non-bacterial causes or topical infection early, review clinical image, infection location and radiation results.
Lactate is normal, but the patient is tired: don't assure the increase, monitor the trend and re-measure if symptoms persist.
The CRP tells you the size of inflammation.
Procalcitonin can give you bacteriological inflammation and help you follow up with treatment.
Lactate tells you if tissues are screaming from a lack of lactation even if the signs still “look good”.
