Adrenal Vein Sampling in Primary Aldosteronism: Sensitivity and Specificity of Basal Adrenal Vein to Peripheral Vein Cortisol and Aldosterone Ratios to Confirm Catheterization of the Adrenal Vein.

PURPOSE: To assess the sensitivity and specificity for ratios of adrenal vein cortisol level (Ca) to peripheral vein cortisol level (Cp), adrenal vein aldosterone level (Aa) to peripheral vein aldosterone level (Ap), and combined cortisol and aldosterone levels ("combined ratio") for the detection of successful adrenal vein catheterization ("selectivity") in adrenal vein sampling (AVS) without adrenocorticotropic hormone (ACTH) injection at different cutoff values. MATERIALS AND METHODS: This retrospective study was approved by the institutional review board, and informed consent was waived. AVS was performed in 160 consecutive patients (49 women and 111 men; mean age, 53.6 years) between December 1989 and January 2014. Cortisol and aldosterone levels were measured in samples from the adrenal veins and left iliac vein every 5 minutes, two times before (basal) and three times after intravenous cosyntropin (ACTH 1-24) injection. Selectivity was defined by Ca/Cp or Aa/Ap ratio of at least 5 in at least one sampling after ACTH administration. Sensitivity and specificity for the detection of selective adrenal vein catheterization were calculated for basal Ca/Cp ratio, Aa/Ap ratio, and combined ratios for three cutoff values reported in the literature. The McNemar test was used to assess differences in sensitivity and specificity to detect selective adrenal vein catheterization. RESULTS: The sensitivity and specificity for the cutoff values of at least 3, at least 2, and at least 1.1 for the detection of AVS selectivity were respectively 50.4% and 100%, 70.8% and 100%, and 98.5% and 76.9% for Ca/Cp ratio; 61.3% and 100%, 70.8% and 100%, and 94.2% and 53.8% for Aa/Ap ratio; and 75.2% and 100%, 88.3% and 100%, and 99.3% and 46.2% for combined ratios (sensitivity at the ≥2 cutoff value: P < .0001 for combined ratio vs Ca/Cp ratio and for combined ratio vs Aa/Ap ratio). CONCLUSION: Basal combined ratio has the best sensitivity for the detection of AVS selectivity at all cutoff values, and for all ratios, the cutoff value of at least 2 has the best sensitivity for 100% specificity.

In vivo imaging of retinal ganglion cell axons within the nerve fiber layer.

Purpose. Optic nerve injury causes loss of retinal ganglion cells (RGCs) and their axons. The reduction in RGC counts over time in axonal injury is well studied, but the correlation with the timing of anterograde and retrograde axonal degeneration is less clear. The authors longitudinally imaged RGC axons stained with a chloromethyl derivative of fluorescein diacetate (CMFDA) in live rats after optic nerve injury. Methods. Optic nerves were transected. Three days later CMFDA was intravitreously injected. Confocal scanning laser ophthalmoscopy was performed daily, and mean fluorescence intensity and the number of CMFDA bundles were calculated. RGC soma survival was studied after retrograde fluorescence labeling. Retinal nerve fiber layer (RNFL) thickness was evaluated histologically. Results. CMFDA-positive RGC axon bundles could be imaged in vivo. Axons lost 68% +/- 29% of their fluorescence by 7 days after transection compared with 25% +/- 21% in nontransected eyes. The number of labeled axon bundles decreased by 61% +/- 28% at 7 days after transection compared with 26% +/- 9% in nontransected eyes. The number of retrograde-labeled RGCs detected in vivo declined by 53% at 7 days and by 76% at 14 days after transection. RGC soma and CMFDA axon counts decreased most rapidly between 5 and 7 days after transection. Histologic examination demonstrated a reduction in RNFL thickness 7 days after transection. Conclusions. Intravitreal CMFDA can be used to longitudinally monitor RGC axons within the RNFL in vivo. Imaging the disappearance of retrograde-labeled RGC somas and axons indicates that axonal and somal degeneration occur in parallel after axotomy.