Use of Dried Blood Smears for Detection of Feline Hemoplasmas Using Real-Time PCR
The objective of this study was to determine the sensitivity and specificity of real-time PCR for feline hemoplasmas when applied to DNA extracted from dried blood smears, in comparison to that for DNA extracted from larger blood samples. Blood samples were collected into EDTA tubes from 310 cats with possible or suspected hemoplasmosis, and dried blood smears from each sample were prepared. DNA was extracted from blood smears and a 160-µL aliquot of each blood sample with a robotic extractor, and subjected to real-time PCR for 18S DNA, and 'Candidatus Mycoplasma haemominutum' (Mhm), Mycoplasma haemofelis (Mhf), and 'Candidatus Mycoplasma turicensis'(Mtc) DNA. Using the results for whole blood as the gold standard, the sensitivity of each assay for Mhm, Mhf, and Mtc was 49/67 (74%), 11/13 (85%), and 11/20 (55%), respectively. The specificity of each assay was 239/249 (96%), 292/292 (100%), and 285/285 (100%), respectively. Where possible, whole blood samples should be submitted for detection of feline hemoplasmas using real-time PCR. The improved sensitivity of real-time PCR on blood smears for Mhf compared with that for the other hemoplasma species may reflect the higher organism burdens associated with infection with this species.