High specificity of spot urinary free metanephrines in diagnosis and prognosis of pheochromocytomas and paragangliomas by HPLC with electrochemical detection.

BACKGROUND: The metanephrines (MNs) in plasma and urine were proposed as biomarkers for the diagnosis of pheochromocytomas and paragangliomas (PPGLs). However, plasma free MNs and 24h urinary fractionated MNs were not satisfactory enough in specificity for the diagnosis of PPGLs. Moreover, the collection of 24h urine was inconvenient. This work examined the diagnostic and prognostic efficiency of free MNs in spot urine for PPGLs. METHODS: We measured free MNs concentration in spot urine and plasma of 28 PPGLs patients and 155 control subjects by HPLC with electrochemical detection. Postoperative free MNs levels in spot urine and plasma of 14 PPGLs patients were also determined. Creatinine (Cr) concentration was used for the correction of urine volume. RESULTS: The specificity of spot urinary free MNs/Cr in the diagnosis of PPGLs was significantly higher than that of plasma free MNs [normetanephrine (NMN), 98.7% (95.4%-99.8%) vs 93.0% (87.4%-96.6%); metanephrine (MN), 93.6% (88.5%-96.9%) vs 84.5% (77.5%-90.0%)]. Meanwhile, the positive likelihood ratios for spot urinary free NMN/Cr and MN/Cr were 69.21 and 13.29, compared with 12.68 and 5.30 for plasma free NMN and MN, respectively. For the PPGLs patients underwent surgery, the plasma free MNs level appeared an abnormal elevation and yielded false-positive results for some patients. Our findings were validated in an independent cohort, resulting in the specificity of 100% for both urinary free NMN/Cr and MN/Cr, and 97.3% and 83.8% for plasma free NMN and MN, respectively. CONCLUSIONS: Spot urinary free MNs/Cr, superior to plasma free MNs, presented a promising biomarker for the diagnosis and prognosis of PPGLs.

Direct electrochemical measurement of metanephrines in spot urine samples for the diagnosis of phaeochromocytomas.

Metanephrines (MNs) were suggested as a potential first-line biochemical index for the diagnosis of phaeochromocytomas (PHEO). In this study, we developed a simple electrochemical method for the quantitative measurement of MNs in spot urine samples. As MNs contain a hydroxyphenyl group, they could be oxidized at a certain potential to quinines, which could be further detected by the differential pulse voltammetry (DPV) method using unmodified screen-printed carbon electrode (SPCE). Meanwhile, the solid phase extraction (SPE) technique was used to eliminate the matrix effect in the samples. Consequently, free MNs from the extracted urine sample were screened in a linear range from 0.25 mg/L to 12.5 mg/L. The lowest limit of quantification (LLOQ) for MNs was 0.25 mg/L and the limit of detection (LOD) was 0.05 mg/L. Both the precisions and recoveries were sufficient for clinical applications. The urine samples from 22 patients with PHEO and 63 controls were analyzed by the proposed method. The area under the ROC curve was 0.981 (95% CI, 0.958-1.000) with the sensitivity of 95.5% and the specificity of 92.4% at the cut-off value of 0.404 mg/L in these urine samples. Overall, the proposed method provides a cost-effective, rapid and simple tool for clinical diagnosis of PHEO.

Association between serum bile acid profiles and gestational diabetes mellitus: A targeted metabolomics study.

BACKGROUND: Given the potential influence of aberrant bile acid metabolism on glucose homeostasis, we hypothesized that serum bile acid metabolism is altered in gestational diabetes mellitus (GDM). We characterized the metabolic profiling changes of serum bile acids in GDM and to find the potential biomarkers for the diagnosis and differential diagnosis of GDM. METHODS: Based on ultrahigh performance liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry, a targeted metabolomics study that involved targeted and untargeted screening techniques was performed to explore the changes in serum bile acid metabolism of GDM cases, intrahepatic cholestasis of pregnancy (ICP) cases and healthy controls. RESULTS: There were 3 significantly different profiling of serum bile acids for GDM, ICP and controls. Compared to the controls, GDM individuals demonstrated significant increases in 8 bile acid species, including 2 dihydroxy conjugated, 1 trihydroxy unconjugated and 5 sulfated bile acids. ß-muricholic acid (ß-MCA) and di-2 were well-suited to use as the metabolic markers for the diagnosis and differential diagnosis of GDM, respectively. CONCLUSIONS: These preliminary findings revealed the protective effect of body against cytotoxicity via elimination of increased sulfated bile acids and aberrant enzyme activity participated in the cycle ß-MCA→hyodeoxycholic acid (HDCA) of the bile acid metabolism pathway for the women with GDM, which gave us further insights into the etiology and pathophysiology of GDM.

Indirect electrochemical detection for total bile acids in human serum.

Bile acids level in serum is a useful index for screening and diagnosis of hepatobiliary diseases. As bile acids concentration is closely related to the degree of hepatobiliary diseases, detecting it is a vital factor to understand the stage of the diseases. The prevalent determination for bile acids is the enzymatic cycling method which has low sensitivity while reagent-consuming. It is desirable to develop a new method with lower cost and higher sensitivity. An indirect electrochemical detection (IED) for bile acids in human serum was established using the screen printed carbon electrode (SPCE). Since bile acids do not show electrochemical signals, they were converted to 3-ketosteroids by 3-α-hydroxysteroid dehydrogenase (3α-HSD) in the presence of nicotinamide adenine dinucleotide (NAD(+)), which was reduced to NADH. NADH could then be oxidized on the surface of SPCE, generating a signal that was used to calculate the total bile acids (TBA) concentration. A good linear calibration for TBA was obtained at the concentration range from 5.00µM to 400µM in human serum. Both the precisions and recoveries were sufficient to be used in a clinical setting. The TBA concentrations in 35 human serum samples by our IED method didn't show significant difference with the result by enzymatic cycling method, using the paired t-test. Moreover, our IED method is reagent-saving, sensitive and cost-effective.

Quantification of ethanol in plasma by electrochemical detection with an unmodified screen printed carbon electrode.

Simple, rapid and accurate detection of ethanol concentration in blood is very crucial in the diagnosis and management of potential acute ethanol intoxication patients. A novel electrochemical detection method was developed for the quantification of ethanol in human plasma with disposable unmodified screen-printed carbon electrode (SPCE) without sample preparation procedure. Ethanol was detected indirectly by the reaction product of ethanol dehydrogenase (ADH) and cofactor nicotinamide adenine dinucleotide (NAD(+)). Method validation indicated good quantitation precisions with intra-day and inter-day relative standard deviations of ≤9.4% and 8.0%, respectively. Ethanol concentration in plasma is linear ranging from 0.10 to 3.20 mg/mL, and the detection limit is 40.0 µg/mL (S/N > 3). The method shows satisfactory correlation with the reference method of headspace gas chromatography in twenty human plasma samples (correlation coefficient 0.9311). The proposed method could be applied to diagnose acute ethanol toxicity or ethanol-related death.