Does a positive Anaplasma phagocytophilum (A. phagocytophilum) deoxyribonucleic acid (DNA) polymerase chain reaction (PCR) test confirm a diagnosis of anaplasmosis?

From the Guidelines

A positive Anaplasma phagocytophilum DNA PCR test is a highly specific diagnostic tool for anaplasmosis, and it confirms the diagnosis of this disease. This molecular test directly detects the genetic material of the bacterium in the patient's blood, making it highly reliable for active infection diagnosis 1. According to the guidelines for the diagnosis of tick-borne bacterial diseases in Europe, a positive PCR result with subsequent sequencing of the amplicons demonstrating Anaplasma-specific DNA in blood is one of the criteria for confirmed human anaplasmosis 1.

Key Considerations

• PCR testing is most sensitive during the first week of illness before antibiotic treatment has begun 1.
• Treatment should not be delayed while awaiting test results if anaplasmosis is clinically suspected 1.
• The recommended treatment is doxycycline 100 mg twice daily for 10-14 days for adults, with weight-based dosing for children 1.
• Early treatment is crucial as anaplasmosis can become severe or life-threatening if left untreated 1.
• Clinical symptoms such as fever, headache, muscle pain, and laboratory findings like thrombocytopenia, leukopenia, and elevated liver enzymes should also be considered in the overall diagnostic assessment 1.

Diagnostic Approach

• A thorough clinical history and physical examination are essential in diagnosing anaplasmosis 1.
• Laboratory tests, including PCR and serology, should be used to confirm the diagnosis 1.
• In endemic areas, treatment is often initiated based on clinical suspicion before laboratory confirmation is available 1.

Treatment and Management

• Doxycycline is the recommended treatment for anaplasmosis, and it should be started as soon as possible after diagnosis 1.
• The duration of treatment is typically 10-14 days, but it may be longer in severe cases 1.
• Patients with anaplasmosis should be monitored closely for signs of complications, such as respiratory failure, cardiac problems, and neurological symptoms 1.

From the Research

Diagnosis of Anaplasmosis

A positive Anaplasma phagocytophilum DNA PCR test can confirm the presence of the bacteria, but it may not necessarily confirm a diagnosis of anaplasmosis. The following points should be considered:

• A PCR test can detect the DNA of A. phagocytophilum, but it may not distinguish between pathogenic and non-pathogenic strains 2.
• A study found that PCR testing is the most commonly used direct diagnostic test to diagnose human granulocytic anaplasmosis, but serologic testing performed at the time of presentation has limited sensitivity 3.
• Culture and other direct detection methods, such as microscopic blood smear examination, can also be used to diagnose anaplasmosis, and culture had the highest yield among the direct tests evaluated in one study 4.
• Co-infections with other tick-borne pathogens, such as Borrelia burgdorferi, can occur, and A. phagocytophilum may be present in early Lyme borreliosis characterized by erythema migrans 5.
• A sample-to-answer direct real-time PCR test can detect A. phagocytophilum DNA in whole-blood specimens with high positive and negative percent agreement compared to standard-of-care methods 6.

Key Considerations

• A positive PCR test result should be interpreted in the context of clinical symptoms and other diagnostic tests.
• The presence of A. phagocytophilum DNA does not necessarily confirm a diagnosis of anaplasmosis, and other diagnostic methods may be necessary to confirm the diagnosis.
• Co-infections with other tick-borne pathogens should be considered in the diagnosis and treatment of anaplasmosis.