Objective—To estimate receiver-operating characteristic
(ROC) curves for a competitive ELISA (c-ELISA)
that is used in serodiagnosis of brucellosis in water
buffalo and cattle, to determine the most appropriate
positive cutoff value for the c-ELISA in confirmation of
infection, and to evaluate species differences in
Sample population—Sera from 4 herds of cattle
(n = 391) and 4 herds of water buffalo (381).
Procedure—Serum samples were evaluated for
Brucella-specific antibodies by use of a c-ELISA. On
the basis of previous serologic test results, iterative
simulation modeling was used to classify animals as
positive or negative for Brucella infection without the
use of a gold standard. Accuracy of c-ELISA for diagnosis
of infection was compared between cattle and
water buffalo by comparison of areas under ROC
Results—A positive cutoff value of 30% inhibition for
c-ELISA yielded sensitivity and specificity estimates,
respectively, of 83.9 and 92.6% for cattle and 91.4 and
95.4% for water buffalo. A positive cutoff value of
35% inhibition yielded sensitivity and specificity estimates,
respectively, of 83.9 and 96.2% for cattle and
88.0 and 97.4% for water buffalo. Areas under ROC
curves were 0.94 and 0.98 for cattle and water buffalo,
Conclusion and Clinical Relevance—ROC curves
can be estimated by use of iterative simulation methods
to determine optimal cutoff values for diagnostic
tests with quantitative outcomes. A cutoff value of
35% inhibition for the c-ELISA was found to be most
appropriate for confirmation of Brucella infection in cattle
and water buffalo. (Am J Vet Res 2003;64:57–64)
Objective—To estimate sensitivity and specificity of
4 commonly used brucellosis screening tests in cattle
and domestic water buffalo of Trinidad, and to compare
test parameter estimates between cattle and
Animals—391 cattle and 381 water buffalo.
Procedure—4 Brucella-infected herds (2 cattle and 2
water buffalo) and 4 herds (2 of each species) considered
to be brucellosis-free were selected. A minimum
of 100 animals, or all animals > 1 year of age, were
tested from each herd. Serum samples were evaluated
for Brucella-specific antibodies by use of standard
plate agglutination test (SPAT), card test (CT),
buffered plate agglutination test (BPAT), and standard
tube agglutination test (STAT). A Bayesian approach
was used to estimate sensitivity and specificity of
diagnostic tests without the use of a gold standard,
assuming conditional independence of tests.
Results—Sensitivity and specificity estimates in cattle,
respectively, were SPAT, 66.7 and 98.9; CT, 72.7
and 99.6; BPAT, 88.1 and 98.1; and STAT, 80.2 and
99.3. Corresponding test estimates in water buffalo,
respectively, were SPAT, 51.4 and 99.3; CT, 90.4 and
99.4; BPAT, 96.3 and 90.7; and STAT, 75.0 and 98.8.
Sensitivity of the CT and specificity of the BPAT were
different between cattle and water buffalo with at
least 95% probability.
Conclusions and Clinical Relevance—Brucellosis
serologic test performance varied by species tested,
but BPAT had the highest sensitivity for screening cattle
and water buffalo. Sensitivity and specificity of
more than 2 screening tests can be estimated simultaneously
without a gold standard by use of Bayesian
techniques. (Am J Vet Res 2002;63:1598–1605)
Objective—To develop an orthotopic model of canine osteosarcoma in athymic rats as a model for evaluating the effects of stereotactic radiotherapy (SRT) on osteosarcoma cells.
Animals—26 athymic nude rats.
Procedures—3 experiments were performed. In the first 2 experiments, rats were injected with 1 × 106 Abrams canine osteosarcoma cells into the proximal aspect of the tibia (n = 12) or distal aspect of the femur (6). Tumor engraftment and progression were monitored weekly via radiography, luciferase imaging, and measurement of urine pyridinoline concentration for 5 weeks and histologic evaluation after euthanasia. In the third experiment, 8 rats underwent canine osteosarcoma cell injection into the distal aspect of the femur and SRT was administered to the affected area in three 12-Gy fractions delivered on consecutive days (total radiation dose, 36 Gy). Percentage tumor necrosis and urinary pyridinoline concentrations were used to assess local tumor control. The short-term effect of SRT on skin was also evaluated.
Results—Tumors developed in 10 of 12 tibial sites and all 14 femoral sites. Administration of SRT to rats with femoral osteosarcoma was feasible and successful. Mean tumor necrosis of 95% was achieved histologically, and minimal adverse skin effects were observed.
Conclusions and Clinical Relevance—The orthotopic model of canine osteosarcoma in rats developed in this study was suitable for evaluating the effects of local tumor control and can be used in future studies to evaluate optimization of SRT duration, dose, and fractionation schemes. The model could also allow evaluation of other treatments in combination with SRT, such as chemotherapy or bisphosphonate, radioprotectant, or parathyroid hormone treatment.
To assess the repeatability of equine 18F–sodium fluoride (18F-NaF) positron emission tomography (PET) findings, and to evaluate the ability of PET to monitor the progression of areas of increased radiopharmaceutical uptake (IRU) in the fetlocks of Thoroughbred racehorses.
25 racehorses with clinical signs related to fetlock injuries.
This study is a prospective, longitudinal clinical study. Twenty-five racehorses (54 fetlocks) underwent three 18F-NaF PET scans 6 weeks apart. The first 18F-NaF PET scan was performed at the start of a 12-week period of rest from racing (lay-up). Areas of IRU in the fetlock joints were quantified using maximal standardized uptake values (SUVmax) and were graded by 2 experienced observers. Statistical comparisons were made between scans to detect changes in IRU grade and SUVmax over time.
Standing PET findings were repeatable, with 131/149 (88%) areas of IRU identified on the initial scans seen again at the 6-week follow-up scan. The palmar/plantar condyles were the sites most commonly presenting with IRU, followed by the proximal sesamoid bones. Overall, 65% of fetlocks demonstrated improvement in IRU grade during the 12-week period of rest from racing. Areas of higher IRU grade took longer to resolve than the lower graded areas.
Standing PET findings in the racehorse fetlock were repeatable. The SUV-based grading system may be helpful when determining appropriate lay-up duration for Thoroughbred racehorses. PET may be used to monitor areas of the fetlock involved in catastrophic breakdown injuries in Thoroughbred racehorses.