Rickettsia PCR

Bacterial/ Viral

Report in 168Hrs

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No Fasting Required

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Detects rickettsial DNA.

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Rickettsia PCR - Comprehensive Medical Test Information Guide

1. Why is it done?
- Test Purpose: Rickettsia PCR (Polymerase Chain Reaction) is a molecular diagnostic test that detects and identifies Rickettsia bacterial DNA in patient specimens (blood, tissue, or fluids). This highly sensitive and specific test enables rapid identification of rickettsial infections.
- Primary Indications: Diagnosis of rickettsial infections including Rocky Mountain Spotted Fever (RMSF), Epidemic Typhus, Endemic Typhus, Scrub Typhus, and Q Fever
- Clinical Presentations: Patients presenting with fever, rash, headache, muscle aches, and exposure to ticks or mites; suspected tick-borne illness in endemic regions
- Timing: Performed during acute phase of illness (first 5-7 days of symptoms when bacterial load is highest); particularly useful for early diagnosis before serological markers appear
- Specimen Types: Whole blood (EDTA), tissue biopsies (skin eschar, rash lesions), cerebrospinal fluid (meningitis cases), or respiratory secretions
2. Normal Range
- Normal Result: NEGATIVE or NOT DETECTED Indicates absence of Rickettsia DNA in the specimen; rules out active rickettsial infection
- Abnormal Result: POSITIVE or DETECTED Confirms presence of Rickettsia species DNA; indicates active or recent rickettsial infection
- Result Reporting: Qualitative results (Positive/Negative/Not Detected); some laboratories may provide cycle threshold (Ct) values for quantitative analysis (lower Ct values indicate higher bacterial load)
- Equivocal Results: May require repeat testing or confirmation with additional molecular targets (genus-specific vs. species-specific primers)
3. Interpretation
- Positive Result Interpretation: Confirms active rickettsial infection; species identification (if available) guides specific diagnosis; warrants immediate antimicrobial therapy (typically doxycycline); indicates need for public health notification in some regions
- Negative Result Interpretation: Rules out rickettsial infection if collected during acute phase; does not exclude infection if collected late in disease course (after bacterial clearance from blood); may indicate alternative diagnosis needed; early negative result does not preclude infection onset
- Sensitivity & Specificity: PCR exhibits high sensitivity (85-100% depending on species and specimen type) and specificity (95-100%); superior to culture for rapid diagnosis; blood PCR most reliable in first week of illness
- Factors Affecting Results: Timing of specimen collection relative to symptom onset (optimal: days 1-7); specimen type and quality; presence of PCR inhibitors; prior antibiotic therapy may reduce bacterial load; HIV/immunocompromised patients may have altered bacterial kinetics
- Clinical Correlation: Results must be interpreted within clinical context; positive result in symptomatic patient with epidemiological risk factors confirms diagnosis; negative result does not exclude infection if clinical suspicion remains high; serological testing (antibodies) recommended for confirmation or late presentation cases
4. Associated Organs
- Primary Systems Affected: Vascular endothelium (primary target); circulatory system; skin (rash manifestation); central nervous system (meningoencephalitis); lungs (pneumonia); kidneys (renal dysfunction); liver (hepatitis); heart (myocarditis); muscles and joints
- Diseases Diagnosed: Rocky Mountain Spotted Fever (Rickettsia rickettsii); Epidemic Typhus (Rickettsia prowazekii); Endemic Typhus (Rickettsia typhi); Scrub Typhus (Orientia tsutsugamushi); Q Fever (Coxiella burnetii); Mediterranean Spotted Fever (Rickettsia conori); other rickettsial spotted fevers
- Complications from Infection: Acute respiratory distress syndrome (ARDS); disseminated intravascular coagulation (DIC); thrombocytopenia; myocarditis with arrhythmias; acute kidney injury (AKI); meningitis; encephalitis; gangrene of extremities; multi-organ failure; death (10-20% mortality if untreated RMSF)
- Pathophysiology: Rickettsiae replicate in endothelial cells causing vasculitis; leads to increased vascular permeability, thrombosis, and tissue necrosis; widespread microvascular inflammation accounts for multi-organ involvement
- Risk Factors for Severe Disease: Delayed diagnosis/treatment; advanced age; male gender; immunocompromise (HIV, transplant); genetic glucose-6-phosphate dehydrogenase (G6PD) deficiency; comorbid conditions (diabetes, hypertension); severe infection at presentation
5. Follow-up Tests
- Serological Testing: Indirect immunofluorescent antibody (IFA) assay for IgM and IgG; complement fixation test; useful for confirmation in late presentation (>7 days illness); IgM indicates acute/recent infection; recommended when PCR negative but clinical suspicion high
- Complementary Molecular Testing: Species-specific PCR if initial PCR positive but species unclear; 16S rRNA gene sequencing for species identification; tissue PCR if blood PCR negative but high clinical suspicion
- Clinical Chemistry Follow-up: Complete blood count (CBC) to assess thrombocytopenia, anemia, leukopenia; comprehensive metabolic panel (CMP) to evaluate liver enzymes (AST, ALT), renal function (creatinine, BUN); coagulation studies (PT, INR, PTT, fibrinogen) to assess for DIC
- Imaging & Additional Tests: Chest X-ray if pneumonia suspected; ECG if myocarditis or arrhythmias considered; lumbar puncture with CSF analysis if meningitis/encephalitis suspected; echocardiography if cardiac involvement indicated
- Monitoring During Treatment: Repeat CBC and CMP at 5-7 days to assess treatment response and organ function recovery; clinical reassessment for defervescence and symptom resolution; monitoring for treatment complications (doxycycline photosensitivity, esophageal irritation)
- Long-term Follow-up: Convalescent serology (second antibody sample at 2-4 weeks) showing 4-fold rise in titer confirms diagnosis; annual screening if occupational exposure continues; assessment for long-term sequelae in severe cases
6. Fasting Required?
- Fasting Requirement: NO - Fasting is NOT required for Rickettsia PCR testing. This is a molecular diagnostic test that only requires blood collection and is independent of nutritional status.
- Patient Preparation: No special preparation needed; patient may eat and drink normally; no fasting period required; can be tested at any time of day
- Specimen Collection Instructions: Blood collected in EDTA (purple-top) tube; proper venipuncture technique required; specimen should be labeled clearly with patient identifiers and date/time of collection; blood PCR optimal within first 7 days of symptom onset for highest sensitivity
- Medications: NO medications need to be avoided for this test; patient may continue all regular medications; doxycycline or other antibiotics can be started or continued regardless of test timing; test results not affected by medication use
- Specimen Handling: Specimen should be transported to laboratory promptly (ideally within 24 hours); refrigerate if delay expected (do not freeze); maintain proper chain of custody documentation; some laboratories may prefer fresh specimen for optimal sensitivity
- Precautions for High-Risk Specimens: Rickettsia organisms are hazardous; specimens should be handled with appropriate biosafety measures (BSL-3 recommended); staff must use personal protective equipment; skin biopsy specimens must be properly fixed and handled following institutional biosafety protocols

How our test process works!