A 120-Minute Saline Infusion Test for the Confirmation of Primary Aldosteronism: A Pilot Study

BACKGROUND

The saline infusion test (SIT) to confirm primary aldosteronism requires infusing 2 L of normal saline over 240 minutes. Previous studies raised concerns regarding increased blood pressure and worsening hypokalemia during SIT. We aimed to evaluate the diagnostic applicability of a SIT that requires 1 L of saline infusion over 120 minutes.

METHODS

A cross-sectional study, including all patients in a large medical center who underwent SIT from 1 January 2015 to 30 April 2023. Blood samples were drawn for baseline renin and aldosterone (t = 0) after 2 hours (t = 120 min) and after 4 hours (t = 240 min) of saline infusion. We used ROC analysis to evaluate the sensitivity and specificity of various aldosterone cut-off values at t = 120 to confirm primary aldosteronism.

RESULTS

The final analysis included 62 patients. A ROC analysis yielded 97% specificity and 90% sensitivity for a plasma aldosterone concentration (PAC) of 397 pmol/L (14 ng/dL) at t = 120 to confirm primary aldosteronism, and an area under the curve of 0.97 (95% CI [0.93, 1.00], P < 0.001). Almost half (44%) of the patients did not suppress PAC below 397 pmol/L (14 ng/dL) at t = 120. Of them, only one (4%) patient suppressed PAC below 276 pmol/L (10 ng/dL) at t = 240. Mean systolic blood pressure increased from 140.1 ± 21.3 mm Hg at t = 0 to 147.6 ± 14.5 mm Hg at t = 240 (P = 0.011).

CONCLUSIONS

A PAC of 397 pmol/L (14 ng/dL) at t = 120 has high sensitivity and specificity for primary aldosteronism confirmation.

Captopril challenge test: an underutilized test in the diagnosis of primary aldosteronism

Primary aldosteronism (PA) is the most common cause of endocrine hypertension and is often underdiagnosed. This condition is associated with increased cardiovascular morbidity and mortality in comparison to age and blood pressure matched individuals with essential hypertension (EH). The diagnostic pathway for PA consists of three phases: screening, confirmatory testing, and subtyping. The lack of specificity in the screening step, which relies on the aldosterone to renin ratio, necessitates confirmatory testing. The Endocrine Society's clinical practice guideline suggests four confirmatory tests, including the fludrocortisone suppression test (FST), saline suppression test (SST), captopril challenge test (CCT), and oral sodium loading test (SLT). There is no universally accepted choice of confirmatory test, with practices varying among centers. The SST and FST are commonly used, but they can be resource-intensive, carry risks such as volume overload or hypokalemia, and are contraindicated in severe/uncontrolled HTN as well as in cardiac and renal impairment. In contrast, CCT is a safe and inexpensive alternative that can be performed in an outpatient setting and can be applied when other tests are contraindicated. Despite its simplicity and convenience, the variability in captopril dose, testing posture, and diagnostic threshold limit its widespread use. This narrative review evaluates the diagnostic accuracy of the CCT across different populations, addresses controversies in its usage, and proposes recommendations for its use in the diagnosis of PA. Furthermore, suggestions for future research aimed at promoting the wider utilization of the CCT as a simpler, safer, and more cost-effective diagnostic test are discussed.

Efficacy of Oral Furosemide Test for Primary Aldosteronism Diagnosis

Context

Confirmatory tests represent a fundamental step in primary aldosteronism (PA) diagnosis, but they are laborious and often require a hospital environment due to the risks involved.

Objective

To evaluate the efficacy of oral furosemide as a new confirmatory test for PA diagnosis.

Methods

We prospectively evaluated the diagnostic performance of 80 mg of oral furosemide in 64 patients with PA and 22 with primary hypertension (controls). Direct renin concentration (DRC) was measured before, and 2 hours and 3 hours after the oral furosemide. In addition, the oral furosemide test was compared with 2 other confirmatory tests: the furosemide upright test (FUT) and saline infusion test (SIT) or captopril challenge test (CCT) in all patients with PA.

Results

The cut-off of 7.6 µU/mL for DRC at 2 hours after oral furosemide had a sensitivity of 92%, specificity of 82%, and accuracy of 90% for PA diagnosis. In 5 out of 6 controls with low-renin hypertension, which might represent a PA spectrum, renin remained suppressed. Excluding these 6 controls with low-renin hypertension, the DRC cut-off of 10 µU/mL at 2 hours after oral furosemide had a sensitivity of 95.3%, specificity of 93.7% and accuracy of 95% for PA diagnosis. DRC after 3 hours of oral furosemide did not improve diagnostic performance. Using the cut-off of 10 µU/mL, the oral furosemide test and the FUT were concordant in 62 out of 64 (97%) patients with PA. Only 4 out of 64 cases with PA (6.4%) ended the oral furosemide test with potassium <3.5 mEq/L. Hypotension was not evidenced in any patient with PA during the test.

Conclusion

The oral furosemide test was safe, well-tolerated and represents an effective strategy for PA investigation.

Captopril challenge test in the diagnosis of primary aldosteronism: consistency between 1- and 2- h sampling

Objective

To examine the consistency of plasma aldosterone concentration at 1 and 2 h in the captopril challenge test (CCT) and to explore the possibility of replacing 2-h aldosterone concentration with 1-h aldosterone concentration for diagnosis of primary aldosteronism (PA).

Methods

This retrospective analysis included a total of 204 hypertensive patients suspected of having PA. Subjects received oral captopril challenge at 50 mg (25 mg if the systolic blood pressure was <120 mmHg), and plasma aldosterone concentration and direct renin concentration were measured at 1 and 2 h afterward (chemiluminescence immunoassay Liaison® DiaSorin, Italy). Sensitivity and specificity were used to reflect the diagnostic performance of 1-h aldosterone concentration using 2-h aldosterone concentration (11 ng/dl as the cutoff) as the reference. A receiver operating characteristic curve analysis was also conducted.

Results

Among the 204 included patients [median age of 57.0 (48.0-61.0) years, 54.4% men], a diagnosis of PA was established in 94 patients. Aldosterone concentration in the patients with essential hypertension was 8.40 (interquartile range 7.05-11.00) ng/dl at 1 h and 7.65 (5.98-9.30) ng/dl at 2 h (P < 0.001). In patients with PA, aldosterone concentration was 16.80 (12.58-20.50) ng/dl at 1 h and 15.55 (12.60-20.85) ng/dl at 2 h (P > 0.999). At a cutoff of 11 ng/dl, the sensitivity and specificity of using 1-h aldosterone concentration to diagnose PA were 87.2% and 78.2%, respectively. A higher cutoff of 12.5 ng/ml increased specificity to 90.0% but decreased sensitivity to 75.5%. A lower cutoff of 9.3 ng/ml increased sensitivity to 97.9% but decreased specificity to 65.4%.

Conclusions

When diagnosing PA with CCT, 1-h aldosterone concentration could not be used to replace 2-h aldosterone concentration.

Evaluation of Phenotypic Tests to Detect Extended-Spectrum β-Lactamase (ESBL)-Producing Klebsiella oxytoca Complex Strains

Klebsiella oxytoca complex (KoC) species may overproduce their chromosomal class A OXY β-lactamases, conferring reduced susceptibility to piperacillin-tazobactam, expanded-spectrum cephalosporins and aztreonam. Moreover, since clavulanate maintains its ability to inhibit these enzymes, the resulting resistance phenotype may falsely resemble the production of acquired extended-spectrum β-lactamases (ESBLs). In this work, a collection of 44 KoC strains of human and animal origin was characterized with whole-genome sequencing (WGS) and broth microdilution (BMD) susceptibility testing. Comparison of ESBL producers (n = 11; including CTX-M-15 [n = 6] and CTX-M-1 [n = 5] producers) and hyperproducers of OXYs (n = 21) showed certain phenotypic differences: piperacillin-tazobactam (MIC_90s: 16 versus >64 μg/mL), cefotaxime (MIC_90s: 64 versus 4 μg/mL), ceftazidime (MIC_90s: 32 versus 4 μg/mL), cefepime (MIC_90s: 8 versus 4 μg/mL) and associated resistance to non-β-lactams (e.g., trimethoprim-sulfamethoxazole: 90.9% versus 14.3%, respectively). However, a clear phenotype-based distinction between the two groups was difficult. Therefore, we evaluated 10 different inhibitor-based confirmatory tests to allow such categorization. All tests showed a sensitivity of 100%. However, only combination disk tests (CDTs) with cefepime/cefepime-clavulanate and ceftazidime/ceftazidime-clavulanate or the double-disk synergy test (DDST) showed high specificity (100%, 95.5%, and 100%, respectively). All confirmatory tests in BMD or using the MIC gradient strip did not perform well (specificity, ≤87.5%). Of note, ceftazidime/ceftazidime-avibactam tests also exhibited low specificity (CDT, 87.5%; MIC gradient strip, 77.8%). Our results indicate that standard antimicrobial susceptibility profiles can raise some suspicion, but only the use of cefepime/cefepime-clavulanate CDT or DDST can guarantee distinction between ESBL-producing KoC strains and those hyperproducing OXY enzymes.

Copy-number analysis by base-level normalization: An intuitive visualization tool for evaluating copy number variations

Next-generation sequencing (NGS) facilitates comprehensive molecular analyses that help with diagnosing unsolved disorders. In addition to detecting single-nucleotide variations and small insertions/deletions, bioinformatics tools can identify copy number variations (CNVs) in NGS data, which improves the diagnostic yield. However, due to the possibility of false positives, subsequent confirmation tests are generally performed. Here, we introduce Copy-number Analysis by BAse-level NormAlization (CABANA), a visualization tool that allows users to intuitively identify candidate CNVs using the normalized single-base-level read depth calculated from NGS data. To demonstrate how CABANA works, NGS data were obtained from 474 patients with neuromuscular disorders. CNVs were screened using a conventional bioinformatics tool, ExomeDepth, and then we normalized and visualized those data at the single-base level using CABANA, followed by manual inspection by geneticists to filter out false positives and determine candidate CNVs. In doing so, we identified 31 candidate CNVs (7%) in 474 patients and subsequently confirmed all of them to be true using multiplex ligation-dependent probe amplification. The performance of CABANA was deemed acceptable by comparing its diagnostic yield with previous data about neuromuscular disorders. Despite some limitations, we expect CABANA to help researchers accurately identify CNVs and reduce the need for subsequent confirmation testing.

Oral Salt Loading Test is Associated With 24-Hour Blood Pressure and Organ Damage in Primary Aldosteronism Patients

Objective

In the present study, we investigated the most useful confirmatory test for reflecting the severity of primary aldosteronism (PA), by evaluating 24-hour blood pressure (BP), urine albumin, left ventricular mass (LVM), and intima media thickness (IMT).

Methods

This study included 113 patients (80 PA and 33 non-PA hypertensive patients) who were admitted to Oita University Hospital and evaluated using ambulatory blood pressure monitoring (ABPM). First, casual blood pressure (BP) and ABPM parameters were compared between PA and non-PA patients. Second, patients were divided into PA-positive and PA-negative groups based on confirmatory tests, including the saline infusion test (SIT), captopril challenge test (CCT), and oral salt loading test (OSLT), and casual BP and ABPM parameters were compared between the 2 groups. In addition, urine albumin excretion, LVM, and maximum IMT as markers of organ damage were compared between the 2 groups.

Results

The ABPM parameters but not casual BP, were higher in PA patients than in non-PA patients. Nocturnal and 24-hour systolic BP (SBP) in OSLT-positive patients were significantly higher than in OSLT-negative patients. ABPM parameters in other confirmatory tests were not different between the PA-positive and PA-negative groups. Urine albumin excretion in OSLT-positive patients was significantly higher than in the OSLT-negative patients. However, in other confirmatory tests, organ damage markers were not different between the 2 groups.

Conclusion

The OSLT is potentially useful not only for the diagnosis of PA but also for assessment of 24-hour SBP and organ damage, as indicated by urine albumin excretion.

The Clinical Impact of CLIR Tools toward Rapid Resolution of Post-Newborn Screening Confirmatory Testing for X-Linked Adrenoleukodystrophy in California

Since the start of X-linked adrenoleukodystrophy (ALD) newborn screening in California, more than half of the diagnosed cases were found to have an ATP binding cassette subfamily D member 1 (ABCD1) gene variant of uncertain significance (VUS). To determine retrospectively the likelihood that these were true positive cases, we used a web-based post-analytical tool in Collaborative Laboratory Integrated Reports (CLIR). Confirmatory plasma very long-chain fatty-acids (VLCFA) profiles for ALD screen positive infant boys were run through the CLIR ALD tool. We compared the distribution by ABCD1 variant classification (pathogenic, likely pathogenic, VUS, and no variant) with the CLIR tool score interpretation (non-informative, possibly ALD, likely ALD, and very likely ALD) and the current case diagnosis. The study showed that CLIR tool positive interpretations were consistent with 100% of the pathogenic and likely pathogenic variants on the ABCD1 gene if a more conservative guideline was used. The tool interpretations were also consistent with screened cases that were determined to not have disease (our no-disorder group). The CLIR tool identified 19 diagnosed ALD cases with VUS to be potential false positives, representing a 40% reduction among all diagnosed ALD cases with VUS. The reduction could be extended to 65% if a more aggressive threshold was used. Identifying such preventable false positives could alleviate the follow-up burden for patients, their families, and California Special Care Centers.

A Nationwide Antenatal Human T-Cell Leukemia Virus Type-1 Antibody Screening in Japan

Japan has been running a nationwide antenatal human T-cell leukemia virus type-1 (HTLV-1) antibody screening program since 2010 for the prevention of HTLV-1 mother-to-child transmission. As part of the program, pregnant women are invited to take an HTLV-1 antibody screening test, usually within the first 30 weeks of gestation, during regular pregnancy checkups. Pregnant women tested positive on the antibody screening test undergo a confirmatory test, either western blotting or line immunoassay. In indeterminate case, polymerase chain reaction (PCR) is used as a final test to diagnose infection. Pregnant women tested positive on a confirmatory or PCR test are identified as HTLV-1 carriers. As breastfeeding is a predominant route of postnatal HTLV-1 mother-to-child transmission, exclusive formula feeding is widely used as a postnatal preventive measure. Although there is insufficient evidence that short-term breastfeeding during ≤3 months does not increase the risk of mother-to-child transmission compared to exclusive formula feeding, this feeding method is considered if the mother is eager to breastfeed her child. However, it is important that mothers and family members fully understand that there is an increase in the risk of mother-to-child transmission when breastfeeding would be prolonged. As there are only a few clinical studies on the protective effect of frozen-thawed breastmilk feeding on mother-to-child transmission of HTLV-1, there is little evidence to recommend this feeding method. Further study on the protective effects of these feeding methods are needed. It is assumed that the risk of anxiety or depression may increase in the mothers who selected exclusive formula feeding or short-term breastfeeding. Thus, an adequate support and counseling for these mothers should be provided. In addition to raising public awareness of HTLV-1 infection, epidemiological data from the nationwide program needs to be collected and analyzed. In most cases, infected children are asymptomatic, and it is necessary to clarify how these children should be followed medically.

Construction of a predictive scoring system as a guide to screening and confirmation of the diagnosis of primary aldosteronism

BACKGROUND

Primary aldosteronism (PA) is the most frequent cause of secondary hypertension. In Southern Thailand, the aldosterone-renin ratio (ARR) is only available within a small number of tertiary centres, necessitating need for a simple clinical assessment to determine the requirement for ARR.

OBJECTIVE

This study aimed to identify predictive factors for the diagnosis of PA and generate a predictive scoring system (PSS) for use in screening and diagnosis of PA.

PATIENTS AND METHODS

A total of 420 patients aged >15 years with paired plasma aldosterone concentration and plasma renin activity values allowing calculation of ARR were identified from the electronic hospital database between 2011 and 2016.

RESULTS

The overall prevalence of PA was 16.7% (range; adrenal incidentaloma 5.6% to hypokalaemia 30%). Predictive factors for diagnosis of PA were as follows: age <60 years, BMI < 25 kg/m² , presence of diabetes, ≥3 antihypertensive agents, serum sodium ≥ 141 mmol/L and serum potassium < 3.5 mmol/L. A predictive scoring system (PSS) (range -2 to 13) was generated by the coefficients of the variables with ROC curve AUC 0.87 [95% CI: 0.83-0.91]. Using the PSS, a total score <4 provided a robust negative predictive value (sensitivity, 0.97; specificity, 0.48; NPV, 0.99; PPV, 0.27) for PA. In patients at high risk of PA (PAC > 15 ng/dL and PRA < 1.0 ng/mL/hr), a PSS score > 9 had specificity and PPV of 100%, essentially confirming PA in these individuals.

CONCLUSION

The proposed PSS for PA will enable more focused and cost-effective use of ARR screening and confirmatory testing. In our cohort, 40% and 42% of patients would not require ARR screening or confirmatory tests, respectively.

Confirmatory tests for the diagnosis of primary aldosteronism: A systematic review and meta-analysis

OBJECTIVE

Saline infusion test (SIT), captopril challenge test (CCT), fludrocortisone suppression test (FST) and oral sodium loading test (SLT) are recommended by the Endocrine Society's Clinical Practice Guidelines to diagnose primary aldosteronism, but which one is the best remains controversial. We aimed to summarize the available comparative data and evaluate the diagnostic accuracy of these four tests.

DESIGN

We searched PubMed, Embase and the Cochrane Library for relevant studies published between January 1980 and January 2018.

PATIENTS

Eligible studies reported on the accuracy of one or more of the four confirmatory tests in patients suspected of PA.

MEASUREMENTS

Two reviewers independently conducted the data extraction of all selected studies, which consisted of study characteristics and data to estimate the summary receiver operating characteristic (SROC) curve and the corresponding summary area under the curve (SAUC), pooled sensitivity and specificity, diagnostic odds ratios (DOR) with 95% confidence interval (CI).

RESULTS

We identified 26 articles including 3686 patients. Fifteen articles evaluated the diagnostic accuracy of CCT, 10 of SIT, 1 of FST and none of SLT. For CCT, the SAUC was 0.9207, and the pooled sensitivity and specificity were 0.87 (95% CI: 0.84-0.89) and 0.84 (95% CI: 0.81-0.86), respectively. For SIT, the SAUC was 0.9232, and the pooled sensitivity and specificity were 0.85 (95% CI: 0.82-0.87) and 0.87 (95% CI: 0.85-0.89), respectively. For FST, the pooled sensitivity and specificity were 0.87 (95% CI: 0.66-0.97) and 0.95 (95% CI: 0.82-0.99), respectively. Overall, we found no significant differences in the diagnostic accuracy of CCT and SIT.

CONCLUSIONS

CCT and SIT exhibit high and comparable accuracy for diagnosing PA. CCT may be a more feasible alternative as it is safe and much easier to perform.

Point-Counterpoint: What Is the Optimal Approach for Detection of Clostridium difficile Infection?

INTRODUCTIONIn 2010, we published an initial Point-Counterpoint on the laboratory diagnosis of Clostridium difficile infection (CDI). At that time, nucleic acid amplification tests (NAATs) were just becoming commercially available, and the idea of algorithmic approaches to CDI was being explored. Now, there are numerous NAATs in the marketplace, and based on recent proficiency test surveys, they have become the predominant method used for CDI diagnosis in the United States. At the same time, there is a body of literature that suggests that NAATs lack clinical specificity and thus inflate CDI rates. Hospital administrators are taking note of institutional CDI rates because they are publicly reported. They have become an important metric impacting hospital safety ratings and value-based purchasing; hospitals may have millions of dollars of reimbursement at risk. In this Point-Counterpoint using a frequently asked question approach, Ferric Fang of the University of Washington, who has been a consistent advocate for a NAAT-only approach for CDI diagnosis, will discuss the value of a NAAT-only approach, while Christopher Polage of the University of California Davis and Mark Wilcox of Leeds University, Leeds, United Kingdom, each of whom has recently written important articles on the value of toxin detection in the diagnosis, will discuss the impact of toxin detection in CDI diagnosis.

Evaluation of the (1-24) adrenocorticotropin stimulation test for the diagnosis of primary aldosteronism

OBJECTIVE

The purpose of this study was to investigate the diagnostic power of the adrenocorticotropin (ACTH) stimulation test in patients with primary aldosteronism (PA) and those with aldosterone-producing adenoma (APA).

DESIGN

This study was based on a retrospective database analysis.

SUBJECTS AND METHODS

We assessed 158 hypertensive patients with a high plasma aldosterone-to-renin ratio (ARR) including 97 with at least one positive confirmatory test result who did not undergo surgery and comprised a "possible PA" group, 19 with negative results in all tests who were the "non-PA" group, and 41 diagnosed with APA following surgery who were the APA group. The "confirmed PA group" included APA patients and patients from the possible PA group showing both high ARR and hypokalemia. One case was diagnosed as a metastasis.

RESULTS

Receiver-operating characteristic (ROC) analysis showed that the diagnostic accuracy of ACTH test was not very effective in differentiating between APA patients and possible PA and non-PA patients. The optimal cut-off value of maximal plasma aldosterone concentration for differentiating between patient in the confirmed PA group and other patients showed moderate accuracy.

CONCLUSIONS

The ACTH test may not be useful as a screening or confirmatory test, but the test may be useful for differentiating between patients with confirmed PA and the rest of the cohort. The positive finding of the ACTH test may at least support a higher likelihood of lateralizing on adrenal venous sampling.

Brief communication: comparison the diagnostic performance of four HBsAg ELISA kits

BACKGROUND

Comparison of diagnostic efficiency of four ELISA kits for determining HBsAg.

METHODS

Collecting 348 serum samples from clinical laboratory of Renmin Hospital of Wuhan University without specific gender and age requirements, determining HBsAg by the four ELISA kits, simultaneously. Confirmatory test was carried out when the initial results are positive.

RESULTS

329 out of 348 samples results were consistent (94.5%), 152 out of 329 were positive, and 177 out of 329 were negative, and all the positive results can be confirmed; 19 samples were not consistent (5.5%), and only 1 sample was confirmed by the confirmatory test. After calculation, the diagnostic efficiencies of the four ELISA kits (Beijing Wantai, Xiamen Xinchuang, Zhuhai Lizhu, and Shanghai Kehua) were 98.6%, 98.0%, 99.7%, and 97.4%, respectively, the sensitivities were 100%, 99.4%, 99.4%, and 100%, respectively, the specificities were 97.5%, 96.9%, 100%, and 95.4%, respectively, the false positive rates were 2.5%, 3.1%, 0, and 4.6%, respectively, and the false negative rates were 0, 0.6%, 0.6%, and 0, respectively. All the initial absorbencies of the false positive samples were less than 1.0.

CONCLUSION

The diagnostic efficiency of Lizhu is the highest, while Kehua is the lowest. False positive or false negative results would take place in any of the kits, an HBsAg confirmatory test is essential for initially positive samples, especially with absorbance <1.0, because it can exclude most false positives.

Screening and diagnosis of primary aldosteronism

Primary aldosteronism (PA) is the most common cause of mineralocorticoid hypertension. Different studies using the plasma aldosterone concentration (PAC)-plasma renin activity ratio (ARR ratio) for the screening of patients with hypertension, have shown a marked increase in the detection rate of PA. PA is commonly caused by an adrenal adenoma (APA) or idiopathic bilateral adrenal hyperplasia of the adrenal zona glomerulosa (IHA) and, in rare cases, by the inherited condition of glucocorticoid-remediable aldosteronism (GRA). The early diagnosis of PA is important, not only because the forms caused by adrenal adenoma are surgically curable, but also because correlation between the duration of PA and the development of cardiovascular complications has been reported. Patients with resistant and/or severe hypertension, patients with hypokalemia, those with a family history of hypertension and stroke at an early age, or patients with an adrenal incidentaloma should be screened for PA using the ARR ratio. Suspicion of PA owing to a pathological ratio requires confirmatory testing, including fludrocortisone suppression test, saline infusion and captopril challenge. Adrenal gland imaging is important in subtype differentiation (APA vs IHA), but adrenal venous sampling is the gold standard and should be used when other tests prove inconclusive. Genetic testing has facilitated detection of GRA.