A multicentre evaluation of the Elecsys® anti-Müllerian hormone immunoassay for prediction of antral follicle count.

RESEARCH QUESTION: What concentration of anti-Müllerian hormone (AMH) corresponds to an antral follicle count (AFC) >15 for determination of ovarian reserve? DESIGN: A prospective study conducted at 13 US fertility clinics in women aged 21-44 years who presented for AFC evaluation by transvaginal ultrasound. Serum samples were collected at the time of AFC evaluation (menstrual cycle day 2-4). AMH concentrations were measured by the Elecsys® AMH immunoassay; oestradiol and follicle-stimulating hormone (FSH) concentrations were also measured. The serum AMH cut-off able to detect AFC >15 with high sensitivity was determined (derivation cohort). Clinical performance of the AMH assay at the derived cut-off was evaluated (validation cohort). Receiver operating characteristic (ROC) analyses were also performed. RESULTS: In the derivation cohort (n = 306), an optimal serum AMH cut-off value of 1.77 ng/ml was determined to correspond to AFC >15 with 89.63% sensitivity and 69.01% specificity, using the Elecsys AMH assay. In the validation cohort (n = 856), this 1.77 ng/ml cut-off could identify women with an AFC >15 with a sensitivity of 88.34% and a specificity of 68.29%; corresponding positive predictive and negative predictive values were 75.19% and 84.34%, respectively. ROC analyses demonstrated that AMH performed better than oestradiol or FSH in predicting AFC, with area under the curves of 85.7%, 57.1% and 69.7%, respectively, in the validation cohort. CONCLUSION: The Elecsys AMH immunoassay provides a robust and fully automated method to measure serum AMH levels. Women with AMH values below the cut-off of 1.77 ng/ml are unlikely to have AFC >15.

The mechanical role of thrombus on the growth rate of an abdominal aortic aneurysm.

OBJECTIVES: In the decision for surgical repair of abdominal aortic aneurysms (AAAs), the maximum diameter is the main factor. Several studies have concluded that the diameter may not be reliable as rupture risk criterion for the individual patient and wall stress was found to have a higher sensitivity and specificity. The AAA wall stress may also be an influential factor in growth of the AAA. This study investigates the effect of intraluminal thrombus on the wall stress and growth rate of aneurysms, using both idealized and patient-specific AAA models in wall stress computations. METHODS: Idealized AAA models were created for wall stress analysis. Thrombus was modeled as an incompressible linear elastic material and was fixed to the wall. The reduction in wall stress for a range of thrombus volumes and shear moduli was computed. For 30 patient-specific AAA models with varying thrombus volumes, the wall stress was computed with and without thrombus. The diameter growth rate was compared for AAAs with a small and large thrombus volume. The results were compared between the idealized and patient-specific models. RESULTS: The thrombus caused a reduction in wall stress, which was stronger for larger thrombi and higher elastic moduli. Any AAAs with a large thrombus were found to have significant stronger growth in diameter than aneurysms with a small thrombus (P < .01). The stress reduction due to the thrombus showed the same trend for the idealized and patient-specific models, although the effect was overestimated by the idealized models and a considerable variation between patients was observed. CONCLUSION: A larger thrombus in AAA was associated with a higher AAA growth rate, but also with a lower wall stress. Therefore, weakening of the AAA wall, under the influence of thrombus, may play a more imminent role in the process of AAA growth than the stress acting on the wall.