A Diagnostic Algorithm for Detection of Leishmania spp. in Human Fresh and Fixed Tissue Samples
Luciana M Silva-Flannery1, Marcos E de Almeida2, Alexandre J da Silva2
1Infectious Diseases Pathology Branch, Division of High-Consequence Pathogens and Pathology, Centers for Disease Control and Prevention, Atlanta, Georgia.
Summary
Accurate diagnosis of Leishmania infection is crucial for treatment. Polymerase chain reaction (PCR) is best for fresh samples, while immunohistochemistry (IHC) combined with PCR improves detection in fixed tissues.
Area of Science:
- Medical Parasitology
- Diagnostic Microbiology
- Infectious Diseases
Background:
- Leishmaniasis is a significant travel-related parasitic disease in the US.
- Accurate diagnosis is essential for effective treatment, varying by Leishmania species.
- Diagnostic method sensitivity and specificity depend on specimen type and condition.
Purpose of the Study:
- To identify the optimal diagnostic algorithm for detecting Leishmania parasites in both fresh and fixed tissue samples.
- To evaluate parasite cultures, PCR methods, and Leishmania immunohistochemistry (IHC) for diagnostic accuracy.
- To compare the efficacy of different diagnostic methods on fresh versus formalin-fixed tissue specimens.
Main Methods:
- Evaluation of parasite cultures, two PCR methods, and Leishmania IHC on clinical samples received by the CDC (2012-2019).
- Assessment of IHC sensitivity and specificity in fresh specimens.
- Evaluation of diagnostic accuracy for formalin-fixed tissues using PCR and IHC.
Main Results:
- In fresh tissues (n=100), PCR detected Leishmania spp. in 56% of cases, with 80% positive by culture and 59% by IHC.
- In fixed tissues (n=420), IHC and/or PCR detected parasites in 58% of cases; IHC was positive in 96% and PCR in 84% of these.
- Overall parasite detection rates were similar for fresh (56%) and fixed (58%) tissues across all methods.
Conclusions:
- Polymerase chain reaction (PCR) is the most effective method for detecting Leishmania infection in fresh tissue samples.
- For formalin-fixed tissue samples, a combination of immunohistochemistry (IHC) and PCR-based methods increases diagnostic accuracy for Leishmania spp. detection.
- Optimizing diagnostic algorithms is key for accurate Leishmania diagnosis and appropriate patient management.
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