Common cold, runny nose, respiratory infections, or pharyngitis are the most frequent reasons for visiting a family doctor. It is crucial to determine whether the infection is viral or bacterial. Appropriate treatment is selected depending on the type of infection.
Antibiotics only fight bacteria; they do not work against viruses. There is also a possibility of bacterial superinfections as complications after undertreated viral infections.
90% of illnesses for which we visit a family clinic, such as the common cold, flu, and respiratory ailments, are caused by viruses, against which antibiotics are ineffective.
Symptoms of the common cold:
CRP in the common cold most often remains within the normal range (0-8 mg/L) or is slightly elevated (up to 40 mg/L). The symptoms of the common cold are caused by over 200 identified viruses! Treatment for the common cold is limited to symptomatic management; antibiotics should under no circumstances be used!
Symptoms of flu:
In infants and children, additional symptoms may include:
Flu usually runs a relatively mild course, but in specific patient groups, especially those over 65, it can cause complications. CRP levels in flu most often do not rise above the normal range (0-8 mg/L). Furthermore, flu should not be treated with antibiotics! It typically resolves after about one week.
Over 70% (up to 90%) of pharyngitis cases are caused by viruses.
Symptoms of pharyngitis:
CRP varies depending on the cause of the throat infection. If the pharyngitis is caused by a virus (e.g., infectious mononucleosis) – CRP remains within the normal range or most often does not exceed 40.
However, in the case of bacterial throat infection (e.g., streptococci) – CRP is usually high and exceeds 40.
Unfortunately, symptoms such as sore throat, swollen tonsils, weakness, chills, fever, cough, or runny nose are very similar in both viral and bacterial infections. Therefore, it is impossible to differentiate the type of infection based on symptoms alone. Fever can also occur in both bacterial and viral infections.
During viral illnesses such as the common cold and flu, CRP is within the normal range (below 8 mg/L). A higher CRP result (above 40 mg/L) or a high result (100 mg/L) and persistent fever suggest the development of a bacterial infection. The CRP indicator is helpful in diagnosing the type of infection and, consequently, in taking ‘targeted’ therapeutic actions.
So-called rapid CRP tests, available in pharmacies, allow you to independently determine your CRP level within minutes before a doctor’s visit. For infections:
If you want an effective diagnosis of an infection, perform a CRP test before starting treatment.
Most patients perform a CRP test only once – before visiting a doctor. Meanwhile, CRP level is not only a diagnostic tool but primarily an indicator of treatment response.
If CRP does not decrease 48–72 hours after starting antibiotic therapy, it may mean that the antibiotic is not working – for example, the bacteria are resistant, the wrong preparation was chosen, or the infection requires a change in treatment. Without a follow-up CRP measurement, this simply cannot be determined.
This is how proper monitoring of a bacterial infection should look:
On the day of bacterial infection identification, a diagnostic test shows CRP above 40 mg/L, suggesting a bacterial infection. The result helps the doctor decide on antibiotics.
Then, a follow-up measurement is performed 48–72 hours after antibiotic implementation. The CRP value should clearly decrease. No decrease = a signal that the treatment may be ineffective.
Check-up after a week – confirmation of recovery. CRP within the normal range (below 8 mg/L) confirms that the body has overcome the infection. This is a safe time to discontinue antibiotic therapy.
ATTENTION! A recurrence of symptoms after a few days is an alarm signal. Another CRP measurement allows for a quick assessment of whether a new wave of infection or bacterial superinfection has occurred.
One bacterial infection = a minimum of 2–3 CRP measurements. Home testing allows you to monitor treatment independently – without waiting in line at the laboratory, without an additional visit, at any time.
Most flu complications affect the respiratory system (pulmonary complications), but they can also affect other systems (extrapulmonary complications).
Pulmonary complications of flu include:
Extrapulmonary complications affect:
At risk of flu complications are:
Bibliography:
[1] Mrozińska M.: Common Cold – Prophylaxis, Treatment. PHARMACY JOURNAL No. 11 (155) 2006.
[2] Guidelines of the College of Family Physicians in Poland, Flu Prevention and Treatment
[3] Albrecht P., Radzikowski A.: Contemporary Standards for Diagnosis and Treatment of Respiratory Tract Infections, Department of Pediatrics, Medical University of Warsaw.
[4] Sapilak B. et al.: Evaluation of the usefulness of C-reactive protein measurements by semi-quantitative and quantitative methods in the diagnosis of upper respiratory tract infections, Family Medicine & Primary Care Review 2012, 14, 3: 431–433.
[5] Przybyłowski T.: Complications of Flu, Medycyna po Dyplomie 2011(20); 11(188): 85-91.
Diagnostic tests for self-administration. Select a product to learn details, find out how to perform the test and make a purchase on our website
Rapid, at-home blood test for CRP protein levels (virus or bacteria)
