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Ireland JL, Lester A, Banse HE. Factors affecting measurement of basal adrenocorticotropic hormone in adult domestic equids: A scoping review. Vet J 2024; 304:106071. [PMID: 38341024 DOI: 10.1016/j.tvjl.2024.106071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 01/12/2024] [Accepted: 02/01/2024] [Indexed: 02/12/2024]
Abstract
Measurement of basal adrenocorticotropic hormone (ACTH) concentration is the most commonly used diagnostic test for pituitary pars intermedia dysfunction (PPID). Although several pre-analytical and analytical factors have been reported to affect basal ACTH concentrations in equids, the extent to which these have been evaluated in the context of PPID diagnosis is unclear. The objectives of this scoping review were to identify and systematically chart current evidence about pre-analytical and analytical factors affecting basal ACTH concentrations in adult domestic equids. Systematic searches of electronic databases and conference proceedings were undertaken in June 2022, repeated in October 2022 and updated in August 2023. English language publications published prior to these dates were included. Screening and data extraction were undertaken individually by the authors, using predefined criteria and a modified scoping review data extraction template. After removal of duplicates, 903 publications were identified, of which 235 abstracts were screened for eligibility and 134 publications met inclusion criteria. Time of year, exercise, breed/type and transportation were the factors most frequently associated with significant increases in ACTH concentration (n = 26, 16, 13 and 10 publications, respectively). Only 25 publications reported inclusion of PPID cases in the study population, therefore the relationship between many factors affecting basal ACTH concentration and diagnostic accuracy for PPID remains undefined. However, several factors were identified that could impact interpretation of basal ACTH results. Findings also highlight the need for detailed reporting of pre-analytical and analytical conditions in future research to facilitate translation of evidence to practice.
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Affiliation(s)
- J L Ireland
- Department of Equine Clinical Science, Faculty of Health and Life Sciences, The University of Liverpool, Leahurst CH64 7TE, Cheshire, UK.
| | - A Lester
- Department of Equine Clinical Science, Faculty of Health and Life Sciences, The University of Liverpool, Leahurst CH64 7TE, Cheshire, UK
| | - H E Banse
- School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
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Hinrichsen SL, Yuen KY, Dryburgh EL, Bertin FR, Stewart AJ. Short-Term Effects of Temperature and Thyrotropin-Releasing Hormone Stimulation on Adrenocorticotropin Stability in Horses. Animals (Basel) 2022; 12:ani12030324. [PMID: 35158648 PMCID: PMC8833476 DOI: 10.3390/ani12030324] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/11/2022] [Accepted: 01/24/2022] [Indexed: 01/30/2023] Open
Abstract
Pituitary pars intermedia dysfunction (PPID) is diagnosed by increased basal or post thyrotropin-releasing hormone (TRH) stimulation ACTH concentrations. ACTH is known to be unstable; however, the effect of different temperatures and TRH stimulation on equine ACTH stability is poorly described. In total, 15 horses, including 8 PPID positive (ACTH > 35 pg/mL at baseline or >65 pg/mL 30 min after TRH stimulation), were divided into 2 groups: 9, including 5 PPID positive, with basal ACTH concentrations and 6, including 3 PPID positive, with post TRH stimulation ACTH concentrations. Whole blood was stored for 1 h at 4, 20, 30, 40, or 70 °C. After centrifugation, immunoreactive ACTH concentrations were determined using a chemiluminescent assay. Linear mixed effect models were used to detect the effects of temperature, PPID status, and TRH stimulation on the immunoreactive ACTH concentration. Temperature had a significant effect (p = 0.003) on immunoreactive ACTH concentrations, and this effect was greater in PPID-negative horses (p = 0.01), with the changes in immunoreactive ACTH concentrations being slightly unpredictably higher or lower than samples stored at 4 °C. Even at 20 °C, mean immunoreactive ACTH concentrations minimally changed by 5% in PPID horses and 12% in non-PPID horses after 1 h. No significant effect of TRH stimulation was identified. Although ACTH concentrations should ideally be determined from samples kept at 4 °C, samples inadvertently left at temperatures of up to 40 °C can provide valid results if analyzed within 1 h; however, this increases the risks of altered ACTH concentrations, occasionally influencing the diagnosis of PPID.
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Affiliation(s)
- Sophia L. Hinrichsen
- School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia; (S.L.H.); (K.Y.Y.); (F.-R.B.)
| | - Ka Y. Yuen
- School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia; (S.L.H.); (K.Y.Y.); (F.-R.B.)
| | - Elizabeth L. Dryburgh
- Boehringer Ingelheim Animal Health Australia Pty. Ltd., North Ryde, NSW 2113, Australia;
| | - François-René Bertin
- School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia; (S.L.H.); (K.Y.Y.); (F.-R.B.)
| | - Allison J. Stewart
- School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia; (S.L.H.); (K.Y.Y.); (F.-R.B.)
- Correspondence: ; Tel.: +61-7-54601-799
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3
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Thane K, Uricchio C, Frank N. Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses. J Vet Intern Med 2022; 36:770-777. [PMID: 35049089 PMCID: PMC8965261 DOI: 10.1111/jvim.16362] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 01/05/2022] [Accepted: 01/07/2022] [Indexed: 01/21/2023] Open
Abstract
Background Diagnosis of pituitary pars intermedia dysfunction (PPID) using the thyrotropin‐releasing hormone (TRH) stimulation test requires blood collection 10 minutes after TRH injection; it is unknown if small differences in timing affect test results. Objective To determine whether early or late sampling results in a significant (≥10%) difference in plasma adrenocorticotropic hormone (ACTH) concentration compared to standard 10‐minute sampling. Animals Twenty‐four healthy adult horses with unknown PPID status. Methods In this prospective study, subjects underwent a single TRH stimulation test, with blood collected exactly 9 minutes (early), 10 minutes (standard), and 11 minutes (late) after injection. ACTH was measured by chemiluminescent immunoassay. Two aliquots of the 10‐minute plasma sample were analyzed separately to assess intra‐assay variability. Data were reported descriptively and bias was calculated using Bland‐Altman plots. Significance was set at P = .05. Results Minor variability was observed between the paired 10‐minute sample aliquots (range, 0%‐6%; median 3%). Overall variability of early or late samples compared to the corresponding paired (average) 10‐minute standard concentration ranged from 0% to 92% (median 10%). Seventy‐five percent of horses (18/24) tested had at least 1 early or late reading that differed by ≥10% from its corresponding 10‐minute standard concentration, and 21% of horses (5/24) would have a different interpretation of testing result with either early or late sampling. Incidence of ≥10% variability was independent of PPID status (P = .59). Conclusions and Clinical Importance Precise timing of sample collection is critical to ensure accurate assessment of PPID status given the observation of significant variability associated with minor alterations in timing of sample collection.
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Affiliation(s)
- Kristen Thane
- Tufts Cummings School of Veterinary Medicine, Department of Comparative Pathobiology, North Grafton, Massachusetts, USA
| | - Cassandra Uricchio
- University of Massachusetts, Department of Veterinary and Animal Sciences, Amherst, Massachusetts, USA
| | - Nicholas Frank
- Tufts Cummings School of Veterinary Medicine, Department of Comparative Pathobiology, North Grafton, Massachusetts, USA
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Evaluation of the sensitivity and specificity of basal plasma adrenocorticotrophic hormone concentration for diagnosing pituitary pars intermedia dysfunction in horses: A systematic review. Vet J 2021; 275:105695. [PMID: 34099343 DOI: 10.1016/j.tvjl.2021.105695] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 04/12/2021] [Accepted: 05/19/2021] [Indexed: 02/01/2023]
Abstract
Measurement of basal adrenocorticotrophic hormone (ACTH) is currently used to diagnose pituitary pars intermedia dysfunction (PPID) in horses, yet a systematic review of the evidence for its use has not been undertaken. This study aimed to systematically review evidence regarding the sensitivity and specificity of the basal ACTH diagnostic test. Electronic databases were systematically searched in January 2019, September 2020 and January 2021, for English language publications published prior to these dates. Screening, data extraction and quality assessment of publications was undertaken by the authors using predefined criteria. Study design, methodology and information reported in included studies were assessed using Standards for Reporting of Diagnostic Accuracy (STARD) checklists. Risk of bias and applicability were appraised using the Quality Assessment tool for Diagnostic Accuracy Studies (QUADAS-2) quality assessment tool. Due to identified biases and marked between-study variations, meta-analysis was not undertaken. After removal of duplicates, 415 publications were identified, of which 25 were evaluated in full, with 11 of these meeting inclusion criteria. In most studies, basal ACTH was reported to have good sensitivity (overall median 75.5%; interquartile range [IQR], 64.0-86.5%; range, 36.0-100%) and excellent specificity (overall median, 95.2%; IQR, 84.2-98.9%; range, 63.3-100%). However, QUADAS-2 and STARD assessment highlighted that studies did not utilise optimal study design and/or study populations for the evaluation of a diagnostic test and the majority were subject to bias, or provided insufficient information to fully assess possible biases. Based on this review, basal ACTH performed better at ruling out PPID than detecting it.
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Hu K, Stewart AJ, Yuen KY, Hinrichsen S, Dryburgh EL, Bertin FR. The effect of freeze-thaw cycles on determination of immunoreactive plasma adrenocorticotrophic hormone concentrations in horses. J Vet Intern Med 2020; 34:1350-1356. [PMID: 32255541 PMCID: PMC7255672 DOI: 10.1111/jvim.15771] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 03/16/2020] [Indexed: 11/28/2022] Open
Abstract
Background Determination of plasma adrenocotrophic hormone (ACTH) concentration (endogenous or thyrotropin‐releasing hormone [TRH] stimulation test) is the most commonly used diagnostic test for pituitary pars intermedia dysfunction (PPID) in horses. Because ACTH is unstable, samples often are frozen to be shipped to laboratories or to allow for batch analysis of research samples. However, the effect of multiple freeze‐thaw cycles on equine ACTH is unknown. Objective To determine the effects of multiple freeze‐thaw cycles on immunoreactive ACTH concentration. Animals Twenty‐eight horses ranging from 10 to 27 years of age were used. Methods Prospective study. Horses were divided into 4 groups: group 1, PPID‐negative, without TRH stimulation; group 2, PPID‐negative, with TRH stimulation; group 3, PPID‐positive, without TRH stimulation; and group 4, PPID‐positive, with TRH stimulation. Whole blood was collected from each horse at baseline or 30 minutes after TRH stimulation. Immunoreactive plasma ACTH concentration was determined using a chemiluminescence assay. Plasma samples then were frozen at −80°C >24 hours, thawed at 4°C and reanalyzed for 5 freeze‐thaw cycles. Changes in plasma ACTH concentration were analyzed using a linear mixed‐effect model. Results Significant effects of freeze‐thaw cycles (P = .001) and PPID status (P = .04) on plasma ACTH concentration were observed, but no significant effect of TRH stimulation was identified. Conclusions and Clinical Importance The plasma ACTH concentration is altered by freeze‐thaw cycles, and the effect is observed sooner in horses with PPID. To diagnose PPID, multiple freeze‐thaw cycles should be avoided when measuring plasma ACTH concentration.
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Affiliation(s)
- Ke Hu
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Allison J Stewart
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Ka Y Yuen
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Sophia Hinrichsen
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | | | - François-René Bertin
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
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Haffner JC, Neal DL, Hoffman RM, Grubbs ST. Plasma adrenocorticotropic hormone concentration in horses decreases after freezing for 60 days. J Vet Diagn Invest 2019; 31:856-858. [PMID: 31646941 DOI: 10.1177/1040638719882374] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We investigated the stability of adrenocorticotropic hormone (ACTH) in plasma after freezing for different lengths of time. The plasma ACTH concentrations of 12 horses were measured on day 0 (baseline) and over time, after stimulation with thyrotropin-releasing hormone. Samples were stored at -80°C for 3, 7, 30, 60, and 90 d, or at -20°C for 3, 7, 30, and 60 d, or between ice packs at -20°C for 3 and 7 d prior to determination of ACTH concentration. ACTH concentrations were compared to baseline (non-frozen day 0 plasma) for each storage method using a mixed model with repeated measures in which each horse served as its own control and day was the repeated effect. Statistical significance was set at p ≤ 0.05, and 0.05 < p < 0.10 was considered a trend. Plasma ACTH frozen at -20°C or at -80°C resulted in degradation of ACTH compared to baseline samples at 60 and 90 d respectively. There was no degradation of ACTH after 7 d when stored between ice packs, or before 30 d at -20°C, or before 60 d at -80°C.
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Affiliation(s)
- John C Haffner
- Middle Tennessee State University, Murfreesboro, TN (Haffner, Hoffman).,Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO (Neal, Grubbs)
| | - Dwana L Neal
- Middle Tennessee State University, Murfreesboro, TN (Haffner, Hoffman).,Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO (Neal, Grubbs)
| | - Rhonda M Hoffman
- Middle Tennessee State University, Murfreesboro, TN (Haffner, Hoffman).,Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO (Neal, Grubbs)
| | - Steven T Grubbs
- Middle Tennessee State University, Murfreesboro, TN (Haffner, Hoffman).,Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO (Neal, Grubbs)
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Leschke DH, Muir GS, Hodgson JK, Coyle M, Horn R, Bertin FR. Immunoreactive insulin stability in horses at risk of insulin dysregulation. J Vet Intern Med 2019; 33:2746-2751. [PMID: 31617618 PMCID: PMC6872612 DOI: 10.1111/jvim.15629] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 09/20/2019] [Indexed: 01/13/2023] Open
Abstract
Background Diseases associated with insulin dysregulation (ID), such as equine metabolic syndrome and pituitary pars intermedia dysfunction, are of interest to practitioners because of their association with laminitis. Accurate insulin concentration assessment is critical in diagnosing and managing these diseases. Hypothesis/Objectives To determine the effect of time, temperature, and collection tube type on insulin concentrations in horses at risk of ID. Animals Eight adult horses with body condition score >6/9. Methods In this prospective study, subjects underwent an infeed oral glucose test 2 hours before blood collection. Blood samples were divided into ethylenediaminetetraacetic acid, heparinized, or serum tubes and stored at 4 or 20°C. Tubes were centrifuged and analyzed for insulin by a chemiluminescent assay over 8 days. Changes in insulin concentrations were compared with a linear mixed effects model. Results An overall effect of time, tube type and temperature was identified (P = .01, P = 0.001, and P = 0.001, respectively). Serum and heparinized samples had similar concentrations for 3 days at 20°C and 8 days at 4°C; however, after 3 days at 20°C, heparinized samples had significantly higher insulin concentrations (P = .004, P = .03, and P = .03 on consecutive days). Ethylenediaminetetraacetic acid samples had significantly lower insulin concentrations regardless of time and temperature (P = .001 for all comparisons). Conclusions and Clinical Importance These results suggest an ideal protocol to determine insulin concentrations involves using serum or heparinized samples with analysis occurring within 3 days at 20°C or 8 days at 4°C.
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Affiliation(s)
- Dakota H Leschke
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Genevieve S Muir
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Jack K Hodgson
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Mitchell Coyle
- School of Agriculture and Food Sciences, The University of Queensland, Gatton, Queensland, Australia
| | - Remona Horn
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - François-René Bertin
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
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Horn R, Bertin FR. Evaluation of combined testing to simultaneously diagnose pituitary pars intermedia dysfunction and insulin dysregulation in horses. J Vet Intern Med 2019; 33:2249-2256. [PMID: 31498947 PMCID: PMC6766519 DOI: 10.1111/jvim.15617] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 08/21/2019] [Indexed: 01/29/2023] Open
Abstract
Background The thyrotropin‐releasing hormone (TRH) stimulation test and the 2‐step insulin sensitivity test are commonly used methods to diagnose, respectively, pituitary pars intermedia dysfunction (PPID) and insulin dysregulation (ID). Objectives To investigate the diagnostic value of combining the TRH stimulation test and the 2‐step insulin sensitivity test to diagnose PPID and ID simultaneously. Animals Twenty‐seven adult horses, 10 control horses without PPID or ID, 5 horses with PPID only, 5 horses with ID only, and 7 horses with PPID and ID. Methods Randomized prospective study. Horses underwent a TRH stimulation test alone, a 2‐step insulin sensitivity test alone, and combined testing with simultaneous TRH and insulin injection in the same syringe. Data were compared by 2‐way repeated measures analysis of variance and 2 1‐sided tests to demonstrate equivalence. Bland‐Altman plots were generated to visualize agreement between combined and independent testing. Results The effect of combined testing on plasma adrenocorticotropic hormone, blood glucose concentration, or percentage decrease in blood glucose concentration was not significantly different from the effect obtained with independent testing. One control horse appeared falsely positive for PPID, 2 PPID‐only horses appeared falsely positive for ID, and 1 PPID and ID horse appeared falsely negative for ID when tests were performed simultaneously. Bland‐Altman plots supported the agreement between combined and independent testing. Conclusions and Clinical Importance Combining the TRH stimulation test and the 2‐step insulin sensitivity test appears to be a useful diagnostic tool for equine practitioners in the field, allowing testing of a horse for both PPID and ID simultaneously.
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Affiliation(s)
- Remona Horn
- School of Veterinary Science, University of Queensland, Gatton, Queensland, Australia
| | - François-René Bertin
- School of Veterinary Science, University of Queensland, Gatton, Queensland, Australia
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Shepard KN, Haffner JC, Neal DL, Grubbs ST, Pearce GL. Effect of delayed plasma centrifugation on equine adrenocorticotropic hormone concentration. J Vet Diagn Invest 2019; 31:585-587. [PMID: 31246158 DOI: 10.1177/1040638719860877] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Plasma adrenocorticotropic hormone (ACTH) concentration is used in the diagnosis of pituitary pars intermedia dysfunction (PPID) in horses. We enrolled 10 horses, 5 PPID-positive and 5 PPID-negative, in our study, September 20-22, 2016. On day 0, 5 mL of whole blood was collected into each of 6 EDTA tubes and immediately placed in a refrigerator at 7°C. One tube was centrifuged within 15 min of collection, followed by centrifugation of one tube from each horse at 4, 8, 12, 24, and 36 h following collection. At each time, centrifuged plasma was pipetted into 1.5-mL polypropylene tubes and stored at -80°C. None of the plasma samples were turbid, hemolyzed, or icteric. Plasma was shipped frozen with cold packs overnight to the Animal Health Diagnostic Center of Cornell University (Ithaca, NY) for analysis. The percent change from baseline (PCFB) was reported to standardize the data given that baseline values differed. The mean PCFB was 2.8 (95% confidence interval: -2.9%, 7.0%). Neither refrigeration of whole blood for up to 36 h prior to centrifugation nor freezing affected plasma ACTH concentrations significantly.
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Affiliation(s)
- Kayla N Shepard
- Boehringer Ingelheim Vetmedica, St. Joseph, MO (Shepard, Neal, Grubbs).,Middle Tennessee State University, Murfreesboro, TN (Haffner).,Innovative Data Resources, Asheville, NC (Pearce)
| | - John C Haffner
- Boehringer Ingelheim Vetmedica, St. Joseph, MO (Shepard, Neal, Grubbs).,Middle Tennessee State University, Murfreesboro, TN (Haffner).,Innovative Data Resources, Asheville, NC (Pearce)
| | - Dwana L Neal
- Boehringer Ingelheim Vetmedica, St. Joseph, MO (Shepard, Neal, Grubbs).,Middle Tennessee State University, Murfreesboro, TN (Haffner).,Innovative Data Resources, Asheville, NC (Pearce)
| | - Steven T Grubbs
- Boehringer Ingelheim Vetmedica, St. Joseph, MO (Shepard, Neal, Grubbs).,Middle Tennessee State University, Murfreesboro, TN (Haffner).,Innovative Data Resources, Asheville, NC (Pearce)
| | - Greg L Pearce
- Boehringer Ingelheim Vetmedica, St. Joseph, MO (Shepard, Neal, Grubbs).,Middle Tennessee State University, Murfreesboro, TN (Haffner).,Innovative Data Resources, Asheville, NC (Pearce)
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Secombe CJ, Bailey SR, de Laat MA, Hughes KJ, Stewart AJ, Sonis JM, Tan RHH. Equine pituitary pars intermedia dysfunction: current understanding and recommendations from the Australian and New Zealand Equine Endocrine Group. Aust Vet J 2018; 96:233-242. [DOI: 10.1111/avj.12716] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 03/29/2018] [Accepted: 05/02/2018] [Indexed: 12/25/2022]
Affiliation(s)
- CJ Secombe
- College of Veterinary Medicine, School of Veterinary and Life Sciences; Murdoch University; Murdoch Western Australia Australia
| | - SR Bailey
- Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences; The University of Melbourne; Werribee VIC Australia
| | - MA de Laat
- Science and Engineering Faculty; Queensland University of Technology; Brisbane QLD Australia
| | - KJ Hughes
- School of Animal and Veterinary Sciences; Charles Sturt University; Wagga Wagga NSW Australia
| | - AJ Stewart
- Equine Specialist Hospital, School of Veterinary Science; The University of Queensland; Gatton QLD Australia
| | - JM Sonis
- Veterinary Associates Equine and Farm, Karaka; Auckland New Zealand
| | - RHH Tan
- Samford Valley Veterinary Hospital; Samford, QLD Australia
- Discipline of Veterinary Clinical Sciences, College of Public Health, Medical and Veterinary Sciences; James Cook University; Townsville QLD Australia
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Knowles EJ, Moreton-Clack MC, Shaw S, Harris PA, Elliott J, Menzies-Gow NJ. Plasma adrenocorticotropic hormone (ACTH) concentrations in ponies measured by two different assays suggests seasonal cross-reactivity or interference. Equine Vet J 2018; 50:672-677. [PMID: 29247453 DOI: 10.1111/evj.12797] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 11/24/2017] [Indexed: 12/01/2022]
Abstract
BACKGROUND Analysis of plasma adrenocorticotropic hormone concentration [ACTH] aids diagnosis of pituitary pars intermedia dysfunction (PPID). Comparisons of the validated chemiluminescent-immunoassay (CI) and immunofluorescent (IF) assays are limited. OBJECTIVES To compare the results of [ACTH] analysis by CI and IF methods of samples collected in autumn and spring and assess cross-reactivity. STUDY DESIGN Method comparison. METHODS Plasma from nonlaminitic ponies was analysed concurrently using the IF and CI methods in autumn and the following spring. Diagnostic thresholds for the IF method were derived using ROC curves and Youden indices to correspond with CI thresholds. Assay specificity was assessed using commercially available ACTH fragments and degradation products of endogenous ACTH. RESULTS CI and IF methods yielded different results (P<0.001); mean differences (CI-IF), (95% confidence intervals): Autumn (n=99) 38.6 (30.6-46.5) pg/ml, Spring (n=88) 5.1 (3.9-6.3) pg/ml. The association between CI and IF results differed in autumn and spring, consistent with seasonally dependent cross-reactivity or interference. Good (κ=0.66-0.74) agreement was obtained for binary interpretation in spring between IF and CI using thresholds of >24 and >29 pg/ml respectively and in autumn between IF and CI using thresholds of >27 and >47 pg/ml respectively or >33 and >77 pg/ml respectively. Of 88 ponies with both spring and autumn samples, 56 (64%) exceeded a published autumn CI threshold (>47 pg/ml), of which 39 (70%) were below the equivalent threshold (<29 pg/ml) the following spring without treatment. The CI assay showed apparent increases in [ACTH] following addition of CLIP (ACTH 18-39). Degradation of ACTH during storage affected the assays differently. MAIN LIMITATIONS Limited numbers of PPID cases were included. Immunoreactivity of commercially available peptides may differ from their endogenous equivalents. CONCLUSIONS The methods yielded different absolute values but the agreement for binary classification was good. An altered pituitary secretome in autumn that affects apparent [ACTH] values is likely. The Summary is available in Spanish - see Supporting information.
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Affiliation(s)
- E J Knowles
- The Royal Veterinary College, North Mymms, Hatfield, Hertfordshire, UK.,The Bell Equine Veterinary Clinic, Mereworth, Kent, UK
| | | | - S Shaw
- Tosoh Bioscience Ltd, Redditch, Worcestershire, UK
| | - P A Harris
- Equine Studies Group, WALTHAM Centre for Pet Nutrition, Waltham on the Wolds, Leicestershire, UK
| | - J Elliott
- The Royal Veterinary College, North Mymms, Hatfield, Hertfordshire, UK
| | - N J Menzies-Gow
- The Royal Veterinary College, North Mymms, Hatfield, Hertfordshire, UK
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Spelta CW. Equine pituitary pars intermedia dysfunction: current perspectives on diagnosis and management. VETERINARY MEDICINE-RESEARCH AND REPORTS 2015; 6:293-300. [PMID: 30101114 PMCID: PMC6067528 DOI: 10.2147/vmrr.s74191] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Equine pituitary pars intermedia dysfunction (PPID) is a neurodegenerative disease of the hypothalamus, resulting in the loss of dopaminergic inhibition of pars intermedia. An oxidative stress injury of unknown etiology has been suggested to initiate the neurodegeneration. While hypertrichosis (formerly known as hirsutism) is considered pathognomic for advanced disease, the antemortem diagnosis of subclinical and early disease has continued to prove difficult. Numerous tests have been used with varying sensitivities and specificities. The overnight dexamethasone suppression test, originally documented to have 100% sensitivity and specificity in horses with advanced disease, has proven to be less valuable in identifying early disease. Basal plasma adrenocorticotropin concentrations have improved sensitivity and specificity when sampled during the autumn months, and α-melanocyte-stimulating hormone, while not yet commercially available, shows promise as a sensitive and specific single sample test. Recent advances in our knowledge include the strong association between laminitis and hyperinsulinemia, both common clinical signs associated with PPID. The pathogenesis of hyperinsulinemia, laminitis, and their association with this disease is a focus of current research. The dopamine agonist pergolide mesylate is still the mainstay of medical management, with studies on oral bioavailability, pharmacokinetics, and long-term survival rates now published.
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Wright S. Highlights of recent clinically relevant papers. EQUINE VET EDUC 2015. [DOI: 10.1111/eve.12316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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