Abstract and Introduction
Abstract
Objective: Primary aldosteronism (PA) is a common form of secondary hypertension. Adrenal venous sampling (AVS) is the gold standard for subtyping PA. This study aimed to determine whether there is a difference between immunoassays and liquid chromatography-mass spectrometry (LC-MS/MS) methods for measuring cortisol levels that affect the judgement of AVS.
Design: This was a retrospective study.
Patients: Included 72 patients who were diagnosed with PA and had undergone AVS.
Measurements: Patients were grouped according to whether they received adrenocorticotropic hormone (ACTH) stimulation during AVS, and the cortisol results were measured using immunoassay and LC-MS/MS.
Results: There were 48 patients in the without ACTH stimulation group and 24 in the post-ACTH stimulation group during AVS (bilateral adrenal vein cannulation success rate, 56.25% vs. 83.33%). ACTH stimulation was beneficial for increasing the success rate of AVS (p < .001). Immunoassays were linearly correlated with LC-MS/MS when cortisol concentrations were <1750 nmol/L (r = .959, p < .001). When cortisol concentrations were >17,500 nmol/L, no correlation was found between the two methods (p = .093). The two methods were consistent for the detection of cortisol for evaluating the success of cannulation for AVS. Five percent of patients showed discordant lateralization of aldosterone production according to the cortisol LC-MS/MS and immunoassay results in the without ACTH group, and 15% showed discordant lateralization in the post-ACTH group.
Conclusions: The immunoassay method can be used to determine whether cannulation is successful. The final decision for lateralization may be more appropriate based on LC-MS/MS results.
Introduction
Primary aldosteronism (PA) is one of the most common forms of secondary hypertension,[1] caused by an excess of spontaneously produced aldosterone. PA can lead to a series of symptoms, such as hypertension, hypokalaemia and metabolic alkalosis. Cardiovascular and cerebrovascular diseases, especially stroke and atrial fibrillation, occur more frequently in patients with PA than in patients with primary hypertension.[1,2] Therefore, early screening and diagnosis of PA are essential. Patients with a clear diagnosis can be treated with targeted therapy.[3] Once the diagnosis of PA is confirmed, the next step is to classify it. PA is mainly divided into five types: aldosterone-producing adrenocortical adenoma (APA), idiopathic hyperaldosteronism (IHA), primary adrenal hyperplasia (also known as unilateral adrenal hyperplasia, UAH), aldosterone-producing adrenocortical carcinoma and familial hyperaldosteronism. The classification and diagnosis are difficult in clinical practice and affect the choice of treatment. Bilateral adrenal venous sampling (AVS) is the gold standard for identifying unilateral forms of PA, and its sensitivity and specificity are better than those of adrenal computed tomography (CT).[3]
AVS is expensive and invasive, requires considerable technical skill, and is sometimes difficult to interpret.[4] Moreover, there are several other limitations; aldosterone and cortisol are released in bursts from the adrenals, which can yield misleading AVS results due to differences in the timing of blood sampling. To overcome this problem, two methods are used: the bilateral simultaneous cannulation of both adrenal veins[5,6] and the strategy of maximally stimulating hormone secretion with adrenocorticotropic hormone (ACTH; cosyntropin) infusion.[7]
Another significant factor affecting the judgement of AVS results is the detection method for steroid hormones. It is well known that errors in the immunoassays (IAs) may affect the estimation of adrenal steroids, such as aldosterone in the adrenal veins, mainly due to its cross-reactivity with other steroids. Serum steroid profiling by isotopic dilution-liquid chromatography-mass spectrometry (LC-MS/MS) is considered the gold standard for hormone testing.[8]
Investigations into the influence of different detection methods have mainly focused on the aldosterone test[9–14] because of the cross-reactivity between 18-aldosterone and tetrahydroaldosterone in the detection process,[15] and the difference in plasma aldosterone levels can be approximately two-fold by different detection methods.[16] LC-MS/MS makes the detection of plasma aldosterone more stable and specific. A comparative study between LC-MS/MS and radioimmunoassays showed that plasma aldosterone measured by LC-MS/MS was lower than that measured by radioimmunoassay.[17]
Cortisol has a long plasma half-life, and it is believed that the cortisol level is relatively stable between different detection methods. However, some studies have found significant differences in cortisol concentration between IAs and LC-MS/MS.[18,19] Nevertheless, the IA method has a significant benefit in that it is faster than the LC-MS/MS method, and results can be obtained within half an hour. Rapid intraoperative cortisol detection using IAs can help determine whether cannulation is successful during the operation, and it increases the success rate of AVS. However, the IA is greatly affected by protein binding interference and cross-reaction and has a narrow detection range. Cortisol concentration in the adrenal veins may be over 10-fold higher than in the peripheral vein before ACTH stimulation. Current studies have shown that the use of ACTH stimulation may increase the success rate of cannulation,[20] but lateralization will be blunted after ACTH stimulation.[21] However, after ACTH stimulation cortisol concentrations can significantly increase in venous blood, especially in the adrenal vein. Therefore, ACTH stimulation may further affect the cortisol levels detected by the IA. The accuracy of IAs may not satisfy the requirements of the AVS procedure. When lateralization ratios are calculated according to the IA-measured cortisol levels, it will mislead the judgement of the lateralization of aldosterone production and may be one of the important reasons for the blunting of lateralization after ACTH stimulation.
In this study, we divided the patients into ACTH stimulation and nonstimulation groups. We observed the AVS results of the two groups using two detection methods and compared the IA method with LC-MS/MS to detect cortisol's effect on the selectivity index (SI) and lateralization index (LI) and explored suitable cortisol profiling methods in AVS.
Clin Endocrinol. 2022;96(5):680-689. © 2022 Blackwell Publishing
