Pre-test probability and likelihood ratios for clinical findings in canine leishmaniasis

Abstract

CanineleishmaniasisisaparasiticzoonosismainlycausedbyL.infantum;anobligateintracellularprotozoantransmittedbyhaematophagousinsectsofthegenusPhleboto-mus,whichaffectsdogsandwildcanids.Theclinicalimplicationsofthisdiseasearehighlyvariable,sinceinfectedanimalsmayremainasymptomatic(absenceofobserv-ableclinicalsigns)orpresentawidespectrumofclinicalalterationsanddegreesofseverity, including the death of the animal. Symptoms such as lymphadenomegaly,alopecia,weightloss,keratoconjunctivitisandonychogryphosisareusuallythefirstdiagnosticreferenceavailable.Theobjectivesofthisstudyaretoevaluatethevalidity(sensitivity,specificityandlikelihoodratios)anddiagnosticutility(pre-testprobability)oftheclinicalsignscommonlyassociatedwithcanineleishmaniasisbasedonthepreva-lenceintheareaandtoexplorethecombinationofsymptomsthatbestpredictsthediagnosisofcanineleishmaniasis.Itisamatchedcase-controlstudyinthecaninepopu-lationofsouthernSpainbasedonthecomparisonofthefindingscollectedintheclinicalhistoryandtheresultsoftheLeisSCANquantitativeELISA.Atotalof39casesand78controlswereanalysed.Approximately80%oftheinfectedanimalsshowedsignscompatiblewiththedisease.Themostfrequentalterationswerecutaneous(64.1%),systemic(51.3%)andoculo-nasal(30.7%).Themostusefulsignstosupportthisdiagno-siswerealopeciaandepistaxis(LR+6.69and6.0,respectively)(pre-testleishmaniasisprobabilityis≥70%forprevalence≥28%whenalopeciaorepistaxisispresent),fol-lowedbylameness(LR+5.0).Thecombinationsofsignsthatshowedgreatervaliditywere alopecia with hyperkeratosis of the snout and alopecia with onychogryphosis(LR+>10).Noneoftheobservedsignsortheircombinationsresultedusefultoruleoutthediagnosis(LR–0.55to1.15).Theresultsfoundshownotabledifferencesinthediagnosticvalueoftheclinicalsigns,individuallyandincombination,sowebelievethatmedicaldecisionsshouldbebasedontheirdiagnosticvalidity(LR+)andtheestimationofthepre-testandpost-testprobability.