Different range, different task
A typical CRP test is designed to detect overt inflammation and works in the range of tens to hundreds of units. The highly sensitive method measures concentrations tens of times lower - it is in this range that chronic, sluggish inflammation of the vascular wall, which underlies atherosclerosis, manifests itself. A value below 1 mg/l corresponds to low cardiovascular risk, above 3 mg/l - high, regardless of cholesterol level. The indicator is used to clarify the risk in patients with intermediate values, when the decision to initiate preventive therapy is not obvious. An important condition: the test cannot be taken within 2-3 weeks after any infection, injury or surgery - acute inflammation completely covers the baseline level and makes the result uninformative.
Why preparation is so important
The laboratory result is a number, but the correct number can only be obtained if the rules are followed. Eating changes the levels of glucose, lipids and a number of enzymes significantly; physical activity the day before increases CK and AST; smoking affects hormones; time of day is critical for cortisol and testosterone.
Therefore, a “bad analysis” often turns out to be a consequence of impaired preparation, and not an illness, and leads to unnecessary examinations and prescriptions.
General rules for donating blood
- on an empty stomach 8–12 hours, you can drink water
- Eliminate alcohol and intense exercise per day
- no smoking in an hour
- donate blood before physiotherapy, x-rays and massage
- Take medications in advance by agreeing with your doctor
- for hormones in women, take into account the day of the cycle
How to read the result
Reference values depend on the method and equipment of the laboratory, so it is correct to compare results only within the same laboratory. A deviation of a few percent from the normal limit in itself rarely matters - the overall picture and dynamics are important. It is up to the physician to interpret the analysis: an isolated indicator without a clinical context is often misleading.