Amidst the confusion and chaos following covid-19 pandemic, I have often seen patients and their relatives tensed over the reports and investigations ordered by doctors and their relevance. Also, owing to poverty and lack of insurance, many people are not able to afford the investigations which are necessary as a part of treatment. This blog is a compiled data of necessary Covid-19 investigations and their importance. Let’s start with introduction of the disease and their clinical manifestations:
- Corona viruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal.
What are the signs and symptoms of the disease?
- Fever, dry cough, sore throat
- Tiredness, aches and pains
- conjunctivitis, loss of taste or smell
- difficulty breathing or shortness of breath
- Chest pain or pressure.
- RAPID ANTIGEN TEST: It is quick bedside test that gives result within 20 minutes. Once rapid antigen test is positive, it implicates that person is suffering from covid infection. No need to do further RT-PCR test. If it is negative and the person is symptomatic then RT-PCR is advised. Once positive, no need to repeat rapid antigen test after 10 days since the virus stops replicating.
- RT-PCR: It is the gold standard test but the results take minimum 8-12 hours to obtain the results. RT-PCR can detect any kind of strain except the newly discovered Indian variant (B.1.617). It is advisable to get more investigations done and quarantine yourself if you are symptomatic and tested negative.
What is CT value?
In simple words, it is the number of cycles that is required for detecting the virus. CT value above 35 indicates low viral load/infectivity and the value below 24 indicates high viral load and the need for hospitalization.
- COMPLETE BLOOD COUNT: There is decrease in total WBC count with absolute lymphopenia(N=1800-7700/mcl). CRP(N=<8.0 mg/dl) and LDH(N=110-210 units/L) levels are also raised. It is repeated 24-48 hourly.
- RBS: Random blood sugar of covid-19 positive patients(especially those on steroids) is highly raised.
- D-Dimer(<0.5 mcg/dl) and PT-INR(11-15 secs): Raised levels indicate an unusual amount of thrombosis and blood clot. Done after 48-72 hours.
- Ferritin (13-150 ng/ml): Active ferritin production by macrophages and cytokines during inflammation leads to hyperferritinemia. High levels are associated with severe disease and high mortality. ALT(7-56 units/L), AST(N=5-40 units/L) and CPK(N=40-140 units/L) are raised indicating liver and muscle involvement.
- Interleukin-6(<7 pg/ml): Several studies have indicated ‘cytokine storm’ associated with increased release of IL-6. It is generally done in deteriorating condition.
- SARS COV2 Anti Spike protein antibody test: It gives you exact measurement of the antibody titres against SARS CoV-2 virus available in your body against Spike Protein after vaccination or infection.
- CT CHEST: CT chest is done to know the severity of lung involvement in covid positive patients. A lung of covid-19 patient typically shows multifocal bilateral ground glass opacities.
What is CO-RADS scoring?
It is a classification used to determine levels of suspicion of Covid-19 infection.
What is CT severity score?
It is calculated from HRCT chest of a covid-19 positive patient to determine level of severity.
Each lobe of lung is given a score of 5(3 lobes on right and 2 on left). Based on the involvement of each lobe, numbering is done and cumulative score is derived out of 25. Another scoring
Score <8: mild infection
9-15: moderate infection
>15: severe infection.
When to do a CT scan?
CT scan is useful for diagnosing extent of lung involvement in Covid-19 patients. However, consult your doctor before undergoing CT scan. According to AIIMS protocol, HRCT is done in moderate and severe cases if there is worsening of condition. Chest X-ray has no role in diagnosis of mild Covid-19 cases.
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