Topic: Malaria, shigella
Question: Write shortly on the various techniques used in the laborotary diagnosis of malaria.
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Here are the various techniques used in the laboratory diagnosis of malaria:
1. Microscopic Examination of Blood Smears:
•It involves collecting blood from the finger prick and making thin and thick blood smears on slides.
•The slides are then stained using Giemsa or Wright stain which stains the parasites purple against the background red cells.
• Under the microscope, the parasite species and developmental stage can be identified based on morphology.
• Experienced microscopists can achieve high sensitivity and specificity with this test.
• However, it requires specialized equipment and training.
2. Rapid Diagnostic Tests (RDTs):
•RDTs detect malaria antigens in the blood using immuno-chromatographic assays.
•The test strip has a sample pad, conjugate pad and detection regions containing antibodies.
• When blood is added to the sample pad, malaria antigens get captured by antibodies on the detection regions, resulting in visible lines.
• Different parasite antigens can be detected to identify species.
• Results are available within 15-20 minutes without specialized equipment.
• However, the sensitivity is lower compared to microscopy.
3. Molecular Diagnostics like PCR:
•PCR amplifies parasite DNA extracted from blood samples.
•Species-specific primers are used to amplify target genes.
•Real-time PCR uses fluorescent probes to provide quantitative results.
•PCR is highly sensitive and can detect low parasite levels.
• It helps monitor treatment response and detect mixed infections.
• Special equipment and trained personnel are required for PCR.
4.Antigen Detection Tests:
•These tests detect parasite antigens in the blood like HRP2 specific to P. falciparum.
•Both RDTs and ELISA techniques can be used to detect antigens.
•Results are available rapidly but cannot differentiate between current and past infections since antigens may persist after treatment.
5. Antibody-Based Tests like IFA and ELISA:
•They detect malaria-specific antibodies like IgG, IgM and IgE in the blood.
•ELISA is a quantitative assay while IFA uses fluorescence microscopy to visualize antibodies.
• Useful in epidemiological studies to identify malaria exposure.
• Not ideal for acute diagnosis since antibodies take time to develop after infection.
So in summary, microscopy remains the gold standard technique but RDTs, molecular diagnostics and antigen detection tests provide rapid and sensitive alternatives, with their own advantages and limitations. An appropriate combination of tests based on availability and purpose can help achieve an accurate malaria diagnosis.
