Clinical effectiveness of a Bayesian algorithm for the diagnosis and management of heparin-induced thrombocytopenia.

Essentials We previously published a diagnostic algorithm for heparin-induced thrombocytopenia (HIT). In this study, we validated the algorithm in an independent large healthcare system. The accuracy was 98%, sensitivity 82% and specificity 99%. The algorithm has potential to improve accuracy and efficiency in the diagnosis of HIT. SUMMARY: Background Heparin-induced thrombocytopenia (HIT) is a life-threatening drug reaction caused by antiplatelet factor 4/heparin (anti-PF4/H) antibodies. Commercial tests to detect these antibodies have suboptimal operating characteristics. We previously developed a diagnostic algorithm for HIT that incorporated 'four Ts' (4Ts) scoring and a stratified interpretation of an anti-PF4/H enzyme-linked immunosorbent assay (ELISA) and yielded a discriminant accuracy of 0.97 (95% confidence interval [CI], 0.93-1.00). Objectives The purpose of this study was to validate the algorithm in an independent patient population and quantitate effects that algorithm adherence could have on clinical care. Methods A retrospective cohort comprised patients who had undergone anti-PF4/H ELISA and serotonin release assay (SRA) testing in our healthcare system from 2010 to 2014. We determined the algorithm recommendation for each patient, compared recommendations with the clinical care received, and enumerated consequences of discrepancies. Operating characteristics were calculated for algorithm recommendations using SRA as the reference standard. Results Analysis was performed on 181 patients, 10 of whom were ruled in for HIT. The algorithm accurately stratified 98% of patients (95% CI, 95-99%), ruling out HIT in 158, ruling in HIT in 10 and recommending an SRA in 13 patients. Algorithm adherence would have obviated 165 SRAs and prevented 30 courses of unnecessary antithrombotic therapy for HIT. Diagnostic sensitivity was 0.82 (95% CI, 0.48-0.98), specificity 0.99 (95% CI, 0.97-1.00), PPV 0.90 (95% CI, 0.56-0.99) and NPV 0.99 (95% CI, 0.96-1.00). Conclusions An algorithm incorporating 4Ts scoring and a stratified interpretation of the anti-PF4/H ELISA has good operating characteristics and the potential to improve management of suspected HIT patients.

Risk factors associated with Mycobacterium avium subspecies paratuberculosis seropositivity in Canadian dairy cows and herds.

Our objective was to determine the risk factors associated with the seroprevalence of Mycobacterium avium subspecies paratuberculosis (MAP) in a large number of randomly selected Canadian dairy herds, controlling for important confounding variables and co-infections with bovine leukemia virus (BLV), bovine viral diarrhea virus (BVDV) and Neospora caninum (NC). Serum samples from 30 randomly selected cows, where available, in 315 herds from seven provinces were tested for antibodies against BLV, MAP and NC using commercially available enzyme-linked immunosorbant assay (ELISA) test kits, while five unvaccinated cattle >6 months old from each herd were tested for antibodies to BVDV. We used a zero-inflated negative-binomial (ZINB) multivariable model to determine simultaneously the risk factors associated with the count of MAP-seropositive cows in a herd, and the odds of herds having no MAP-seropositive cows as compared to having one or more MAP seropositive cows in a herd. The following factors were significantly positively associated with the count of MAP-seropositive cows: "more than one cow in the maternity pen", "group-housing for pre-weaned calves in winter", "open heifers purchased during the last 12 months", "beef cattle direct (nose-to-nose) contact", "BVDV-seropositive herds (> or = 1 animal with > or = 1:64 titer)" and "BVD vaccination not done properly in calves" (i.e. after 6 months old, animals were not boostered 2-4 weeks after their first killed vaccine, or not given modified live vaccine), with count ratios of 1.7, 2.0, 2.3, 1.9, 1.4 and 1.8, respectively. The variable "BVDV vaccination (modified live) done properly in calves" (i.e. received another modified live vaccination after 6 months as well) was associated with 0.4 times fewer MAP-seropositive cows.

Production effects of pathogens causing bovine leukosis, bovine viral diarrhea, paratuberculosis, and neosporosis.

The primary purpose of this research was to determine associations among seropositivity for bovine leukemia virus (BLV), bovine viral diarrhea virus (BVDV), Mycobacterium avium ssp. paratuberculosis (MAP), and Neospora caninum (NC) and each of 3 outcome variables (305-d milk, fat, and protein production) in Canadian dairy cattle. Serum samples from up to 30 randomly selected cows from 342 herds on monthly milk testing were tested for antibodies against BLV (IDEXX ELISA; IDEXX Corporation, Westbrook, ME), MAP (IDEXX or Biocor ELISA; Biocor Animal Health, Inc., Omaha, NE), and NC (IDEXX or Biovet ELISA; Biovet Inc., St. Hyacinthe, Quebec, Canada). Up to 5 unvaccinated cattle over 6 mo of age were tested for virus-neutralizing antibodies to the Singer strain of type 1 BVDV. Dairy Herd Improvement records were obtained electronically for all sampled cows. Linear mixed models with herd and cow as random variables were fit, with significant restricted maximum likelihood estimates of outcome effects being obtained, while controlling for potential confounding variables. Bovine leukemia virus seropositivity was not associated with 305-d milk, 305-d fat, or 305-d protein production. Cows in BVDV-seropositive herds (at least one unvaccinated animal with a titer > or =1:64) had reductions in 305-d milk, fat, and protein of 368, 10.2, and 9.5 kg, respectively, compared with cows in BVDV-seronegative herds. Mycobacterium avium ssp. paratuberculosis seropositivity was associated with lower 305-d milk of 212 kg in 4+-lactation cows compared with MAP-seronegative 4+-lactation cows. Neospora caninum seropositivity in primiparous cows was associated with lower 305-d milk, fat, and protein of 158, 5.5, and 3.3 kg, respectively, compared with NC-seronegative primiparous cows. There were no interactions among seropositivity for any of the pathogens and their effects on any of the outcomes examined, although the low MAP seroprevalence limited this analysis. Results from this research will contribute to understanding the economic impacts of these pathogens and justify their control.

Diquat poisoning of dairy cattle by topical application.

This case report describes poisoning of dairy cattle from a dermal challenge of 50 to 100 mg/kg body weight diquat. Five of 36 cattle exposed, demonstrated clinical signs of intoxication, dehydration, and death over 5 days. Diquat poisoning of cattle by the dermal route has not previously been reported.

Isotopic analogues as internal standards for quantitative analyses of drugs and metabolites by GC-MS--nonlinear calibration approaches.

In order to achieve accurate quantitation of drugs and metabolites (analytes) in complex matrices, 2H- (and less commonly 13C-) labeled analogues of the analytes are now routinely adapted as the internal standards (IS) using linear calibration models to fit data generated by selected ion monitoring gas chromatography-mass spectrometry (GC-MS) protocols. In this study, the effects of cross-contribution (contribution of the IS to the intensity of the ion designated for the analyte and vice versa) on the linearity of the calibration data are examined. Nonlinear approaches that may address this problem are also studied. Two ion pairs (one with least and one with significant cross-contribution) from each of the following analyte/IS pairs are used as the exemplar systems for this study: butalbital/13C4-butalbital, butalbital/2H5-butalbital, secobarbital/13C4-secobarbital, and secobarbital/2H5-secobarbital. Analyte/IS ion intensity ratios of a series of standard solutions are correlated with the analyte/IS concentration ratios using one-point, multiple-point (unweighted and weighted) linear, and hyperbolic functions. The one-point calibration approach produces excellent calibration results in treating data derived from ion pairs with no significant cross contribution. In cases where significant cross-contribution exists, results derived from the one-point approach show, as expected, significant deviations at both ends of the concentration range. With the cross-contribution phenomenon accounted for, the hyperbolic calibration model is clearly more effective in fitting calibration data at both the lower and higher analyte concentration ends, thus significantly lowering the detection limit and extending the calibration range to a higher level. However, the calibration range cannot be extended indefinitely. At the low concentration end, noise-to-signal ratio and the cross-contribution of the IS to the intensity of the ion designated for the analyte, however insignificant, will incrementally reduce the quality of the observed ion intensity and intensity ratio data. At the high concentration end, detection saturation and the cross-contribution of the analyte to the intensity of the ion designated for the IS, however insignificant, will incrementally decrease the "slope" of the calibration curve. Thus, acceptable sensitivity (increase in analyte/IS ion-pair intensity ratio per unit increase in analyte concentration) of the calibration curve will become the limiting factor.

Headroom requirements for horses in transit.

Horses intended for slaughter in Western Canada are frequently transported in double-deck trailers, where headroom may be restricted. Poll and withers height was estimated from type photographs of various horse breeds. The headroom required by Canadian legislation and codes of practice may not be sufficiently restrictive to protect the welfare of sport type horses when transported.

Comparison of minimum space allowance standards for transportation of cattle by road from 8 authorities.

Space allowance for animals in transit is a consistent concern in many countries developing codes of practice and regulations to assure humane treatment of food producing animals. Describing minimum space allowance requirements for cattle in transit has proven to be difficult, as the space required increases as the animal grows. Loading pressure, defined as weight of live animal per unit area, has proven to be a clear method of communicating with transporters and inspection staff what the maximum safe stocking limit is based on individual animal weight. The loading density recommendations in the Canadian code of practice for beef cattle are compared with other standards by using loading pressure charts as a visual aid. Loading pressure charts are recommended in preference to a tabular format to describe the minimal space allowed per animal for cattle transported by road.

A comparison of gross pathology, histopathology, and mycobacterial culture for the diagnosis of tuberculosis in elk (Cervus elaphus).

Using the isolation of Mycobacterium bovis as the reference standard, this study evaluated the sensitivity, specificity and kappa statistic of gross pathology (abattoir postmortem inspection), histopathology, and parallel or series combinations of the two for the diagnosis of tuberculosis in 430 elk and red deer. Two histopathology interpretations were evaluated: histopathology I, where the presence of lesions compatible with tuberculosis was considered positive, and histopathology II, where lesions compatible with tuberculosis or a select group of additional possible diagnoses were considered positive. In the 73 animals from which M. bovis was isolated, gross lesions of tuberculosis were most often in the lung (48), the retropharyngeal lymph nodes (36), the mesenteric lymph node (35), and the mediastinal lymph nodes (16). Other mycobacterial isolates included: 11 M. paratuberculosis, 11 M. avium, and 28 rapidly growing species or M. terrae complex. The sensitivity estimates of gross pathology and histopathology I were 93% (95% confidence limits [CL] 84.97%) and 88% [CL 77.94%], respectively, and the specificity of both was 89% [CL 85.92%]). The sensitivity and specificity of histopathology II were 89% (CL 79.95%) and 77% (CL 72.81%), respectively. The highest sensitivity estimates (93-95% [CL 84.98%]) were obtained by interpreting gross pathology and histopathology in parallel (where an animal had to be positive on at least one of the two, to be classified as combination positive). The highest specificity estimates (94-95% [CL 91-97%] were generated when the two tests were interpreted in series (an animal had to be positive on both tests to be classified as combination positive). The presence of gross or microscopic lesions showed moderate to good agreement with the isolation of M. bovis (Kappa = 65-69%). The results showed that post-mortem inspection, histopathology and culture do not necessarily recognize the same infected animals and that the spectra of animals identified by the tests overlaps.

An abattoir study of tuberculosis in a herd of farmed elk.

The purpose of this study was to examine the prevalence and distribution of grossly visible lesions of tuberculosis in a herd of 344 North American elk (Cervus elaphus) depopulated during a three-month period in 1991. Abattoir inspection detected mycobacterial lesions in 134 (39.8%) of the 337 animals received for slaughter. The prevalence of lesions increased with the age of the animals. Lesions were predominantly suppurative rather than caseous, and mineralization was less evident than in tuberculous lesions in cattle. Lesions occurred predominantly in lymph nodes, and lungs were the only organs in which mycobacterial lesions were found. The distribution of lesions suggested that aerosol transmission was the most significant means of spread of the disease within the herd. Giant liver flukes (Fascioloides magna) were observed in approximately 80% of the adult elk.

Effect of inhibitors of glutathione S-transferase on glyceryl trinitrate activity in isolated rat aorta.

We investigated the role of glutathione S-transferases (enzymes known to biotransform organic nitrates) in the vascular action of glyceryl trinitrate (GTN). Relaxation of phenylephrine-contracted rat aortic strips was assessed in the presence or absence of the glutathione S-transferase inhibitors Basilen Blue, bromosulfophthalein, Rose Bengal, hematin, chlorotriphenyltin, and (octyloxy)benzoylvinylglutathione. Whereas none of the inhibitors increased the EC50 for GTN relaxation, glutathione S-transferase activity in the 100,000 x g supernatant fraction of rat aorta was inhibited markedly by most of the inhibitors. In addition, GTN-stimulated activation of aortic guanylyl cyclase in broken-cell preparations was attenuated by all of the glutathione S-transferase inhibitors, suggesting a direct inhibitory action on guanylyl cyclase. In other experiments using aortic strips preexposed to phenylephrine, the inhibitors had no effect on GTN-induced cyclic GMP accumulation or on vascular biotransformation of GTN. In contrast, both Basilen Blue and bromosulfophthalein significantly inhibited GTN-induced relaxation of K(+)-contracted aortic strips, and Basilen Blue significantly inhibited GTN biotransformation in aortic strips preexposed to 25 mM K+. This may be due to a more favourable electrochemical gradient for entry of the inhibitors into membrane-depolarized tissues. We conclude that vascular glutathione S-transferases play a role in mediating the vasodilator actions of GTN in intact tissues in vitro, but that this appears to depend upon the nature of the contractile agent used in such studies.

Hemostatic studies in racing standardbred horses with exercise-induced pulmonary hemorrhage. Hemostatic parameters at rest and after moderate exercise.

The purpose of this study was to determine whether a defect in hemostasis might be a factor in the etiology of exercise-induced pulmonary hemorrhage (EIPH). Hemostatic parameters were evaluated in 22 EIPH-positive and ten EIPH-negative racing horses while in a rested state. Nineteen EIPH-positive and ten EIPH-negative horses were further evaluated just before and immediately after a 15 min exercise period on a 260 m oval track. When EIPH-positive and EIPH-negative horses were compared at rest, there was no significant difference in any of the coagulation and fibrinolytic parameters studied. There was however, a significant difference in platelet function as assessed by aggregometry. The platelets from affected horses were significantly less responsive than those from nonaffected horses when exposed in vitro to the platelet agonists adenosine diphosphate, collagen and platelet activating factor. Exercise tended to increase the packed cell volume and factor VIII/von Willebrand factor and to decrease platelet aggregation responses to low concentrations of adenosine diphosphate. These effects of exercise however were quantitatively similar in both EIPH-positive and EIPH-negative horses. Reduced platelet function may therefore be a contributing factor in the bleeding characteristic of horses with EIPH.

Effects of sodium bicarbonate and potassium chloride drinking water supplementation. 1. Performance and exterior carcass quality of broilers grown under thermoneutral or cyclic heat-stress conditions.

Two broiler trials were conducted using two environmentally controlled chambers. From 4 to 8 wk of age in Trial 1, and from 5 to 8 wk of age in Trial 2, male broilers were grown under either constant environmental conditions [25 C, 50% relative humidity (RH)], or a daily cyclic heat stress period (4 h of 35 to 38 C, 40% RH). One of four water solutions was provided to each of 16 pens per chamber: 1) 5% NaHCO3: 2) .5% KCl; 3) .5% KCl and NaHCO3, or 4) an unsupplemented control of tap water. Seven-wk body weight, 8-wk weight, weight gain, water consumption, infected feather follicle score, prekill and carcass without giblets weight were all significantly (P less than .05) affected by environmental treatment in both trials. In Trial 1, a significant effect due to water treatment was detected for infected feather follicle score, with control broilers significantly less afflicted than broilers on the other three water treatments. In Trial 2, a significant (P less than .05) temperature treatment effect was detected for abdominal fat pad weight, where differences in fat pad weight were found among water treatments under constant conditions but not under cyclic environmental conditions. These differences in fat pad weight, when expressed as a percentage of carcass weight, were at a probability of .0814. Overall, no appreciable improvements were detected in the broiler production parameters measured under either environmental regimen for the water treatments tested.

Effects of sodium bicarbonate and potassium chloride drinking water supplementation. 2. Meat and carcass characteristics of broilers grown under thermoneutral and cyclic heat-stress conditions.

Two broiler trials were conducted to investigate the effect on post-mortem carcass and meat quality of NaHCO3 and KCl drinking water supplementation under thermoneutral and cyclic heat-stress climatic conditions. Water chill carcass weight change, water- and oven-cooked breast filled yields, and breast meat tenderness were measured. In Trial 1, neither environmental regimen, nor water treatments, nor their interaction was a significant (P less than .05) source of variation for the parameters measured. In Trial 2, environmental regimen was a highly significant (P less than .01) source of variability for chilled carcass weight change; the cyclic heat-stressed broiler carcasses gained more weight than the thermoneutral (control) broiler carcasses during ice-water chilling. Oven-cooked fillet yield was significantly (P less than .05) affected by environmental regimen; fillets from cyclic heat-stressed broilers had lower yields than thermoneutral (control) broiler fillets. Drinking water treatments were a significant (P less than .05) source of variation for breast meat tenderness in Trial 2. Broilers given .5% NaHCO3 from 5 to 8 wk of age had higher shear resistance values than broilers given a combination of .5% NaHCO3 and .5% KCl or tap water-fed controls. Breast meat shear values were negatively correlated (P less than .05) with 8-wk broiler body weight and 5- to 8-wk gain.

Oral rehydration therapy and broiler performance during summer growing conditions.

Two 8-wk broiler trials were conducted during summer growing conditions. Mild heat stress (30 C), as evidenced by panting, was induced by ventilation adjustments. From 4 to 8 wk of age, half of the pens were provided with a .10 strength, human oral rehydration therapy (ORT) solution containing .35 g sodium chloride, .25 g sodium bicarbonate, .15 g potassium chloride, and 4.0 g sucrose/L of drinking water. No significant (P less than .05) differences were found between treatments for 8-wk body weight. Mortality rate during the experiment period (4 to 8 wk) did not differ significantly between treatments in either trial, though it approached significance (P = .0558) in Trial 1 where mortality for broilers given ORT was 3.96% compared with 7.67% for control broilers. Feed efficiency was significantly (P less than .05) better in Trial 1 for ORT broilers, although no significant difference was found between treatments in Trial 2. Posttrial litter moisture measurements showed no significant differences (P greater than .05) between treatments in either trial. A crystalline deposit was observed in the internal filters of the bell-type waterers, which was probably caused by the sucrose (sugar) component of the ORT solution.

Simple nonrebreathing valves for use with large mammals.

Two simple nonrebreathing valves suitable for use with large mammals are described. These valves can be constructed in a reasonably well equipped workshop using materials that are readily available. The resistive pressure of both valves is less than 0.1 kPa at flow rates up to 15 L.s-1. Their main limitation is a relatively large dead space, although the dead space of valve B (290 mL) is less than the dead space of some commercially available valves. Healthy adult horses and cows compensate for the increased dead space by an increase in tidal volume.

Effects of the dwarfing gene (dw) on egg weight, chick weight, and chick weight: egg weight ratio in a commercial broiler strain.

The effects of the dwarfing gene (dw) on egg weight, chick weight, and chick weight: egg weight ratio were studied. Egg weights prior to setting and subsequent chick weights were determined on 1842 chicks from standard-sized broiler dams and 1694 chicks from closely related dwarf dams. Egg weight means were 67.3 and 63.0 g for standard and dwarf dams, respectively. Chick weights expressed as percentage of egg weight were 68.4 and 67.3% for standard and dwarf dam chicks, respectively. Both egg weight and chick weight: egg weight ratio differences were highly significant (P less than .01). Percent hatch weights of male and female chicks, 68.0 and 67.7%, respectively, were also significantly different (P less than .05). Regression analysis of egg weight on chick weight estimated the overall equation: chick weight = -6.13 g + .78 X egg weight. A significant positive linear relationship between chick weight: egg weight ratio and egg weight was detected; males increased more than females and dwarf dam chicks more than standard dam chicks. This suggests that chicks from large eggs utilize egg nutrients more efficiently than those from small eggs. Because the larger eggs come from larger hens, it is speculated that there may be a genetic basis to this phenomenon. It was concluded that egg weight, sex, and dam type each significantly contributed to the variability in chick weight and chick weight: egg weight ratio.