Adrenal Vein Sampling International Study (AVIS Study)

Background. AVS is recommended by the current Endocrine Society Guideline as the gold standard for the identification of the surgically curable subtype of primary aldosteronism (PA).(Funder 2008) However, consensus on the way AVS should be performed and on the interpretation of its results still lacks, as recently pointed out. (Stewart 2010, Auchus 2010) In particular, some centers use the bilateral simultaneous technique, while others perform the sequential catheterization. Moreover, some centers perform AVS during or after using ACTH stimulation, albeit with different doses, and others do not use any stimulation.(Seccia 2009) In addition, some are utilizing the absolute values of plasma cortisol and aldosterone to determinate the lateralization (Nishikawa 2007), whereas others are relying on calculation of the selectivity index to determine the collection of adrenal vein blood, followed by calculation of the and the lateralization index only if bilaterally selective samples were obtained.(Rossi 2008) Moreover, large differences in the cutoffs for establishing selectivity and lateralization exist, which have not been clarified by recent studies that rather added further complexity to this field.(Mulatero 2010) If a consistent degree of success rate can be achieved by having only one or two radiologists performing AVS at each centre, or if more radiologists can become proficient in performing the procedure and consistently achieving adequate results, also remains to be clarified. Finally, some centers perform AVS in all patients who are plausible candidates to adrenalectomy, while other submit to AVS only a small proportion of the patients (Young WJ personal communication).

Thus, it remains unclear which is the proportion of patients with PA who are offered AVS at the different centers, and how many of those who are submitted to AVS ultimately undergo adrenalectomy.

In an era of shrinking budget the issue of cost the issue of costs of the procedure also remains a relevant one when assessing the cost-effectiveness of the diagnostic work-up of PA. A preliminary survey suggests that there are huge variations across different countries in the charges for AVS to both the patients and/or the health care and insurance system.

It is likely that one of the reasons for the lack of consensus on AVS could depend on the facts that: i) no single centre as gathered a number of AVS studies large enough to warrant solid conclusions; ii) there has been no systematic survey of the AVS data that have been generated around the world in this field

Aims of the study. Based on this background, the aims of the AVIS study are those described above.

Study design. To the first aim a questionnaire will be circulated among the centers that are internationally recognized and have published in the field of AVS and have agreed to participate in the study.

The data will be collected and handled at the maximum level of confidentiality under the requirement of the Declaration of Helsinki.

Study selection criteria. Eligible centers will be identified among those that have published in the English literature on AVS or PA (reported variously as observational cohort studies, or clinical trials): Studies will be identified through computer-assisted literature searches of databases, scanning of reference lists, hand-searching of relevant journals, correspondence with authors of relevant reports and consultation with experts in the field.

The inclusion criteria will be the consent of the leading investigator to participate in the data collection.

The only exclusion criteria will be the refusal to participate in the study. The number of adhering and non-adhering centers will be recorded and mentioned in the publications.

Data collection. Data will be collected in an anonymous way on many characteristics at baseline and at subsequent surveys during follow-up. Information on categorical variables, will be systematically re-coded to ensure comparability among studies. For each individual patient, data were sought on the following outcomes: blood pressure and antihypertensive medications at follow-up post-adrenalectomy and on dates of occurrence of cardiovascular events, including non-fatal CHD; non fatal stroke; specific cause mortality (or at least fatal CDH and fatal stroke) and other cardiovascular outcomes. Being a retrospective study, precise details of the diagnostic criteria used for the definition of incident cases will be sought from each centre (as were data on the completeness of follow-up).

Data obtained from each participating study will be checked for internal consistency and any queries that might arrive will clarified with the P.I. of each centre, before harmonization to a standard format.

The content of the data will be unchanged by this process, and computer-generated detailed summary tabulations based will be reviewed and confirmed by collaborators.

Data will be stored securely and anonymously at the coordinating centre.

Statistical analysis will be performed by use of summary statistics after appropriate transformation of the variables that show a skewed distribution as PAC and PCC by means of the SPSS for Mac (vers 18.0), GaphPad and the MedCalc softwares.

Scientific Committee. The leading investigator of each centre contributing at least 50 AVS studies will be invited to participate in the scientific committee of the AVIS study and will have full access to the locked database.

Expected results. Upon completion of the first phase of the study the investigators expect to be able to gather information on the way AVS is being performed around the world and therefore to prepare a first manuscript reporting on the number of AVS per centre, the rate of adrenal vein ruptures during the procedure, the rate of use of simultaneous/sequential AVS catheterization, the number of radiologists that perform AVS and their success rate in the procedure, the rate of use of stimulation test during the perform of AVS, the percentage of PA patients to whom AVS is offered at each center, the rate of calculation of the selectivity index, the lateralization index and the contralateral suppression index and their cutoff limits, the use of AVS studies that are not bilaterally selective for diagnosis and the costs of AVS for the National Health System or Insurance and for the patients.

Upon completion of the database with the individual data the investigators expect to be able to gather > 2000 AVS studies, in a single database. After harmonization of the data, identification of the outliers and of the underlying reasons (by interaction with the leading investigator at each center), the database will be locked. The investigators will then undertake the statistical analysis, which will entail the following variables:

• Demography (sex, age, race);
• Baseline blood pressure (BP) and heart rate (HR) values;
• Serum K+ before AVS;
• Dynamic test during the AVS if any;
• Plasma aldosterone (PAC) and cortisol concentration (PCC) in the infraadrenal inferior vena cava (IVC) and in the right (RAV) and left (LAV) adrenal vein;
• Final diagnosis (bilateral adrenocortical hyperplasia (BAH), unilateral adrenocortical hyperplasia (UAH), aldosterone-producing adenoma (APA), bilateral APA;
• Treatment (adrenalectomy or pharmacological therapy);
• Post-treatment blood pressure (BP) and heart rate (HR) values;
• Post-treatment sK+ ;
• Diagnosis concordance/discordance between imaging (CT or RM) and AVS. Data on the demography, biochemical and hemodynamic features of the patients selected for AVS in the different continents will be obtained and information on the rate of successful catheterization will be generated. The concordance rate of imaging and AVS results will also be determined and the clinical usefulness of the AVS for establishing the indication to adrenalectomy will be ascertained in the largest database available ever.