[Leish-l] Status of PCR for CL diagnosis

[A. Bart]

Dear Hugo,
We found PCR to be more sensitive than microscopy (see table below), BUT you should at least consider for your setting:
- patient population (presentation delay/size & type of lesion)
- parasite population (our population was >40% L. major)
- material used (most of our materials are biopsies, rather than aspirates/scrapings/swabs). Site of sampling is obviously also important.
- DNA isolation methodology
- PCR facilities. We use a strict unidirectional workflow (making PCR mixes>DNA extraction>PCR) with physically separated labs and dUTP/UNG against contamination. You do not want false positives due to amplicon-contamination.
- training of personnel. Our microscopists are dedicated parasitology microscopists in a reference center, a luxury hardly any other lab in our country has. There is a huge difference between having positive microscopy for a given parasite every week or only once a year from an external quality control.

We routinely do microscopy on a smear from one biopsy, use the remainder for PCR and inoculate for culture from a second biopsy directly after sampling. We still do microscopy because we prefer to have (also) a speedy (<1 hour) result from microscopy despite the 70% sensitivity for our population. Our culture is mainly for reference purposes.

Table taken from Bart A, van Thiel PP, de Vries HJ, Hodiamont CJ, Van Gool T. Imported leishmaniasis in the Netherlands from 2005 to 2012: epidemiology, diagnostic techniques and sequence-based species typing from 195 patients. Euro Surveill. 2013;18(30):pii=20544. Article DOI: http://dx.doi.org/10.2807/1560-7917.ES2013.18.30.20544

Cutaneous leishmaniasis
                                pos     neg     nd      tested  sens
PCR                             183     4       0       187     98%
microscopy                      127     47      13      174     73%
culture                         138     29      20      167     83%
micro+culture                   151     15      21      166     91%
micor+PCR                       172     2       13      174     99%
culture+PCR                     164     2       21      166     99%
microscopy+culture+PCR  166     0       21      166     100%


Kind regards,
Aldert

Met vriendelijke groet/With kind regards,
Dr. Aldert Bart
Parasitology Section, Dept Med Microbiol, room L1-106; Academic Medical Center; PO box 22660; 1100DD Amsterdam; The Netherlands;
Tel: +31-20-5663189; Pager: +31-20-5669111 ask for pager 63189; out of office on Friday afternoons.



-----Original Message-----
Van: leish-l-bounces at lineu.icb.usp.br [leish-l-bounces at lineu.icb.usp.br] namens Hugo Valdivia [hvalrod at hotmail.com]
Verzonden: maandag 27 maart 2017 6:30
Aan: Leish-L
Onderwerp: [Leish-l] Status of PCR for CL diagnosis

Dear colleagues,

We have been recently questioned about the use of PCR for CL  diagnosis given that the Peruvian Ministry of health considers microscopy as the standard practice for CL diagnosis. In this sense, I would like to hear your thoughts about the use of PCR for CL diagnosis, specially from those colleagues working in reference diagnostic centers. What I reviewed made me think that there is no a consensus yet on the topic.

Thank you for the information that you can provide and hope to see you in WL6.

Best regards,
Hugo O. Valdivia,  BSc, PhD
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