Fever Panel — Dengue, Malaria & Typhoid Testing in India

The danger of treating fever empirically without testing:: Paracetamol and rest are appropriate for viral fevers, but dengue requires avoiding NSAIDs (ibuprofen, aspirin) which dangerously increase bleeding risk. Malaria requires specific antimalarials. Typhoid requires antibiotics targeting Salmonella Typhi. Getting the diagnosis right matters.

Dengue blood tests::

NS1 Antigen:: The earliest marker. Detectable from Day 1–5 of fever, before antibodies develop. High sensitivity in early disease.

Dengue IgM antibody:: Appears from Day 4–5. Confirms recent dengue infection. Best test if fever has been present > 5 days.

Dengue IgG antibody:: Indicates past infection. Elevated IgG in a second dengue infection increases the risk of severe dengue (Dengue Haemorrhagic Fever).

Complete Blood Count (CBC):: Critical in dengue management. Falling platelet count (thrombocytopaenia) and rising haematocrit (haemoconcentration) are warning signs of progressing disease.

Warning signs requiring immediate hospitalisation::

• Platelet count < 50,000/µL

• Abdominal pain or tenderness

• Persistent vomiting

• Bleeding from gums or nose

• Blood in urine or stools

• Rapid breathing, cold extremities

Malaria Rapid Diagnostic Tests (RDTs)::

Detect parasite antigens in blood within 15–20 minutes. Available at Thyrocare collection centres. Can detect *P. falciparum* (HRP-2 antigen) and *P. vivax* separately.

Peripheral Blood Smear (Gold Standard)::

Blood smear examined under microscope by trained technician. Can identify species, quantify parasitaemia, and monitor treatment response. Requires expertise but is definitive.

Malarial Malaria Antigen (Card Test):: Rapid immunochromatographic test — quick results in under 20 minutes.

Symptoms:: High cyclical fever (every 48–72 hours), rigors (shaking chills), drenching sweats, headache, muscle aches. *Falciparum* malaria can cause cerebral malaria, blackwater fever, and organ failure within 24–48 hours — it is a medical emergency.

Widal Test:: Measures antibodies against S. Typhi O and H antigens. Historically the standard test, but has significant limitations: cross-reactions with other infections, past infections, and vaccines cause false positives. A single Widal is unreliable — only a four-fold rise between two tests (taken 5–7 days apart) is diagnostically significant.

Blood Culture:: The definitive test for typhoid. Detects the bacteria itself. Best collected in the first week of illness before antibiotics are started. Can take 48–72 hours for results.

Typhoid IgM (Typhidot):: Newer rapid antibody test. More specific than Widal. Detects IgM antibodies from Day 4–5.

Leptospirosis:: Bacterial infection (Leptospira spp.) contracted through water or soil contaminated with urine of infected animals (rats, cattle). Common after floods in urban India. Causes fever, severe muscle pain, jaundice, and kidney failure in severe cases. **Test:** Leptospira IgM antibody (ELISA). Paired with LFT and KFT to assess organ involvement.

Chikungunya:: Viral infection spread by Aedes mosquitoes. Causes severe joint pain (debilitating arthralgia), rash, and fever. Joint pain can persist for months. **Test:** Chikungunya IgM antibody — usually positive from Day 3–5 of fever.