A comparison of three diagnostic techniques for the detection of Giardia lamblia in pet dogs
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Verhoeven L. G. A., Faculty of Veterinary Medicine, University of Utrecht, The Netherlands Abstract of Master’s Thesis, Submitted 23 June 2015 A comparison of three diagnostic techniques for the detection of Giardia lamblia in pet dogs The aim of this thesis is to compare 3 different test methods in the detection of Giardia cysts in dog faeces. The population is focused on dogs older than six months. The IFA is used as a golden standard to determine relative sensitivity and specificity for the CSF method and PCR method. The results of this study are useful for veterinary practitioners to determine which method is most fitting for their practice. Based on sensitivity and specificity of tests from previous literature, the PCR and CSF method are not equally qualitatively valuable as the IFA test method. Relative sensitivity for the CSF method according to literature is 34%, relative specificity 92%. Relative sensitivity for the PCR method (real-time PCR) is 100% and relative specificity 98.4% (for these values only one study per test method is used). However, the PCR results are considered highly doubtful. In the execution of this study 359 IFA outcomes and 1065 CSF outcomes have been compared. For the PCR a test batch of only 14 samples of faeces have been collected, therefore conclusions for the PCR method are considered unreliable. The results show that the CSF method cannot be considered equally valuable to the IFA golden standard. Relative sensitivity and specificity of CSF compared to IFA is determined at 24% and 100%. From these results it is concluded that the CSF method is not as able as the IFA to correctly identify faeces from animals that contain Giardia cysts. On the contrary, the results indicate that the CSF method is however equally able to identify faeces that does not contain Giardia cysts. Overall the IFA test method is most reliable, still many factors need to be taken into account when deciding which method is most suitable for the veterinary practice. Preparation time of the slides is longer for the IFA than for CSF. However the IFA preparation time contains waiting time that can be used for other purposes so it is not considered a negative quality. Also, IFA slides are easier to view by unexperienced microscopists. For the CSF method experienced and up-to-date microscopists are needed, otherwise the results are much less reliable. A big advantage of the CSF method is that it can give more information about a patient than the IFA method, as it can detect more parasites than just Giardia cysts. A big disadvantage of the IFA method is that a very specific and expensive microscope is needed. Overall it depends in the time and effort that is put into the microscopists and the financial investment whether the CSF of IFA method is more useful for the individual practices. The IFA method is more practical an efficient but requires expensive equipment. CSF is more difficult to learn, less reliable, but gives more information on a patient than IFA and is more accessible due to lower equipment costs. If there are no experienced microscopists available, a practice can also decide to send samples to qualified laboratories for testing on Giardia cysts.