Feline plasma adrenocorticotropic hormone: validation of a chemiluminescent assay and concentrations in cats with hypercortisolism, primary hypoadrenocorticism and other diseases

Abstract

Objectives The aims of this study were to validate a commercially available chemiluminescent assay for measurement of feline plasma adrenocorticotropic hormone concentration (ACTH), to determine the normal reference interval (RI) of plasma ACTH in healthy cats, to assess plasma ACTH in cats with naturally occurring hypercortisolism (HC), primary hypoadrenocorticism (PH) and other diseases (OD), and to evaluate the effect of aprotinin on plasma ACTH degradation. Methods Forty healthy cats, 10 with HC, 11 with PH and 30 with OD, were included. The chemiluminescent enzyme immunometric assay was evaluated by measurement of intra-assay precision, interassay precision and linearity. The RI for plasma ACTH in healthy cats was established using robust methods. Plasma ACTH of samples collected with and without aprotinin, stored at 4°C and assayed over a 6-day period, was measured. Results The intra-assay coefficients of variance (CVs) ranged from 2.7% to 4.3% and interassay CVs from 3.3% to 10.7%. Dilution studies showed excellent accuracy (R2 >0.99). The RI for plasma ACTH in healthy cats was 32–370 pg/ml. Plasma ACTH was not significantly different between healthy cats and the OD group. Cats with pituitary-dependent hypercortisolism (PDH) and PH had significantly higher plasma ACTH than the other groups. Plasma ACTH did not show significant differences when samples collected with and without aprotinin were compared. Conclusions and relevance The Immulite chemiluminescent assay is a valid technique for measuring plasma ACTH in cats and the RI of plasma ACTH is quite wide. Owing to the low overlap between healthy or OD cats and cats with HC or PH, the measurement of plasma ACTH appears to be useful and should be included in the diagnostic work-up when HC or PH are suspected. Furthermore, the measurement of plasma ACTH may be an accurate test for differentiating PDH from adrenal-dependent hypercortisolism.

Analytical Validation of a New Immunoenzymatic Method for the Measurement of Feline Parathyroid Hormone in Cats with Chronic Kidney Disease

“…This decrease was even more evident after 24 h, discouraging the use of long-time stored samples for PTH measurement in cats. This observation has two possible explanations: firstly, the proteolytic degradation of the molecule could decrease the serum PTH concentration, as reported for other hormones such as adrenocorticotropic hormone [ 23 ]; secondly, the high deviation from the baseline could be attributable to the relatively low concentration of PTH (11.05 pg/mL) in the sera used for the evaluation of storage stability. However, the decrease of 14.5% after 6 h at 4 °C and about 20% after 6 h at 20 °C and after 24 h at 4 °C could be considered acceptable for clinical purposes, especially in cats affected with CKD in which the PTH concentrations are significantly higher [ 19 ].…”

Clinical features and long‐term management of cats with primary hypoadrenocorticism using desoxycorticosterone pivalate and prednisolone

“…Plasma ACTH concentrations were determined by a 2‐site solid‐phase chemiluminescent immunometric assay (DPC Immulite 1 (samples until July 2011), DPC Immulite 1000 (samples from August 2011 to September 2016) or DPC Immulite 2000 (samples from September 2016 until June 2021); Siemens Schweiz AG, Zurich, Switzerland) validated for cats. 17 Plasma was stored at −20°C until assayed. Serum sodium and potassium concentrations were measured with a Cobas c501 chemistry analyzer (Roche Pharma Schweiz AG, Reinach, Switzerland).…”

“…For the determination of plasma endogenous ACTH (9 cats), blood was collected (before ACTH administration) into chilled EDTA‐coated tubes placed on ice and centrifuged at 4°C within 30 minutes. Plasma ACTH concentrations were determined by a 2‐site solid‐phase chemiluminescent immunometric assay (DPC Immulite 1 (samples until July 2011), DPC Immulite 1000 (samples from August 2011 to September 2016) or DPC Immulite 2000 (samples from September 2016 until June 2021); Siemens Schweiz AG, Zurich, Switzerland) validated for cats 17 . Plasma was stored at −20°C until assayed.…”

“…Zurich, Switzerland) validated for cats. 17 Plasma was stored at À20 C until assayed. Serum sodium and potassium concentrations were measured with a Cobas c501 chemistry analyzer (Roche Pharma Schweiz AG, Reinach, Switzerland).…”