Usefulness of FTA® cards as a Pneumocystis-DNA extraction method in bronchoalveolar lavage samples

ABSTRACT

Background FTA® cards (Fast Technology for Analysis of Nucleic Acids) are an alternative DNA extraction method in bronchoalveolar lavage (BAL) samples for Pneumocystis jirovecii molecular analyses. The goal was to evaluate the usefulness of FTA® cards to detect P. jirovecii-DNA by PCR in BAL samples compared to silica adsorption chromatography (SAC). Methods This study used 134 BAL samples from immunocompromised patients previously studied to establish microbiological aetiology of pneumonia, among them 15 cases of Pneumocystis pneumonia (PCP) documented by staining and 119 with other alternative diagnoses. The FTA® system and SAC were used for DNA extraction and then amplified by nested PCR to detect P. jirovecii. Performance and concordance of the two DNA extraction methods compared to P. jirovecii microscopy were calculated. The influence of the macroscopic characteristics, transportation of samples and the duration of the FTA® card storage (1, 7, 10 or 12 months) were also evaluated. Results Among 134 BAL samples, 56% were positive for P. jirovecii-DNA by SAC and 27% by FTA®. All 15 diagnosed by microscopy were detected by FTA® and SAC. Specificity of the FTA® system and SAC were 82.4% and 49.6%, respectively. Compared to SAC, positivity by FTA® decreased with the presence of blood in BAL (62% vs 13.5%). The agreement between samples at 7, 10 and 12 months was 92.5% for FTA®. Positive cases by FTA® remained the same after shipment by mail. Conclusions Results suggest that FTA® is a practical, safe and economical method to preserve P. jirovecii-DNA in BAL samples for molecular studies.

Keywords:

• Pneumocystis jirovecii
• bronchoalveolar lavage
• polymerase chain reaction
• FTA®
• affinity chromatography

Acknowledgements

The authors thank the Sustainability Strategy CODI 2013-2014 of the University of Antioquia. This research was financed jointly by the Departamento Administrativo de Ciencia, Tecnología e Innovación (Colciencias, code 111534319142), the Universidad de Antioquia and the Asociación Colombiana de Enfermedades Infecciosas (ACIN). The funders had no role in the design of the study; in the recollection, analysis and interpretation of the data; in writing the manuscript; or in the decision of sending it for publication.

Disclosure statement

The authors report no conflicts of interest. They deny any link with the trade house that produces or distributes the FTA® cards and they reject any financial, academic or personal interests, directly or indirectly, that may question the validity of the manuscript.