Clinical application of a contingent screening strategy for trisomies with cell-free DNA: a pilot study.

BACKGROUND: Different strategies have been designed for clinical implementation of cell-free DNA (cfDNA) testing. We aimed to evaluate the performance of a contingent strategy based on conventional screening and offering cfDNA to the intermediate-risk group, for the screening for trisomies 21, 18 and 13. Secondary objectives were to assess the uptake of cfDNA in women with intermediate-risk, to evaluate the performance of cfDNA testing, and the preferences of pregnant women with intermediate risk. METHODS: Prospective observational pilot study between February 2016 and March 2017. Singleton pregnancies with a known outcome were included in the study. At the conventional screening (first trimester combined test or second trimester quadruple test) women were classified in high (risk ≥1:250) or low risk (< 1:250). For the study, a contingent strategy was applied: following the conventional screening women were classified into three groups: high risk (risk ≥1:10 or nuchal translucency ≥3 mm), intermediate-risk (risk 1:11 to 1:1500) and low risk (< 1:1500), and a cfDNA test was offered to those at the intermediate risk. RESULTS: For the analysis, 2639 women were included, 2422 (91.8%) had a first trimester combined test and 217 (8.2%) a second trimester quadruple test. There were 5 cases of trisomy 21, 4 of trisomy 18 and none of trisomy 13. For the contingent strategy, the detection rate and false positive rates were 88.9% (8/9) and 1.3% (35/2630), respectively. For the conventional strategy, the detection rate and false positive rates were 66.7% (6/9) and 5.3% (140/2630), respectively. The cfDNA test had a detection rate for trisomy 21 of 100% (3 out of 3), and a false positive rate of 0.2% (1/466). In a survey, 81.8% (374/457) of women in the intermediate-risk group would choose cfDNA testing as the second line test, mainly due to the lack of risk for the fetus. CONCLUSION: A contingent screening strategy for trisomies 21, 18 and 13, based on conventional screening, and offering a cfDNA test to women with a risk between 1:11 to 1:1500, reduced the false positive rate and increased the detection rate for these trisomies. Moreover, this strategy is well accepted by women.

Estudio del zinc en plasma seminal mediante métodos colorimétricos / Evaluation of two colorimetric methods for the determination of zinc in seminal plasma

Objetivos: El objetivo de este estudio es evaluar el posible uso de dos kits comerciales para la determinación colorimétrica de zinc en plasma seminal humano, como alternativa a la compleja metodología analítica de la espectrofotometría de absorción atómica (AAS), y validar la relación entre zinc y citrato en plasma seminal. Pacientes: Ciento sesenta pacientes que acuden al servicio de andrología procedentes, fundamentalmente, de los servicios de esterilidad, urología, endocrinología y oncología con edades comprendidas entre los 17 y 63 años. Métodos: El estudio incluye la comparación del método de referencia para la determinación de zinc en plasma seminal, AAS, y los métodos colorimétricos; la validación de los dos métodos colorimétricos [basados en los cromóforos 2-(5-bromo-2-piridilazo)-5-(N-propil-N-3-sulfopropilamino)-fenol (5-Br-PAPS) y 2-(5-nitro-2-piridilazo)-5-(N-propil-N-sulfopropilamino)-fenol (Nitro-PAPS), respectivamente] para imprecisión, linealidad y límite de cuantificación y el estudio de la correlación entre zinc y citrato. Resultados: Los métodos colorimétricos y la AAS son intercambiables. La imprecisión intradía media (% CV) obtenida con el kit basado en 5-Br-PAPS es de 2,42, y 5,81% con el kit basado en Nitro-PAPS. En el estudio de linealidad, ambos métodos presentan un coeficiente de regresión de 0,999 en concentraciones de zinc entre 10-500 μg/dl, aunque en dicho rango el kit basado en 5-Br-PAPS presenta mejores porcentajes de recuperación. Se observa una correlación positiva significativa entre el zinc y citrato (r = 0,724, p < 0,001). Conclusión: Los métodos colorimétricos representan una buena alternativa a la AAS; el método colorimétrico basado en 5-Br-PAPS muestra mejores prestaciones (AU)

Objectives: The aim of the current study is to evaluate the possible use of two commercial kits for the colorimetric determination of zinc in human seminal plasma as an alternative to the complex analytical methodology of atomic absorption spectrophotometry and to assess the relation between zinc and citrate in seminal plasma. Patients: The study included 160 patients, aged 17 to 63 years, who came to the Andrology service proceeding fundamentally from the Sterility, Urology, Endocrinology and Oncology Departments. Methods: The study included the comparison of the method of reference for the determination of zinc in seminal plasma, atomic absorption spectrophotometry and the colorimetric methods, the validation of both colorimetric methods (based on the chomophores 5-Br-PAPS and Nitro-PAPS, respectively) determining imprecision, linearity and limit of quantification and the correlation study between zinc and citrate. Results: Both colorimetric methods and atomic absorption spectrophotometry are interchangeable. The average within-run variation (%CV) is 2.42% with the 5-Br-PAPS based kit and 5.81% with the Nitro-PAPS based kit. In the linearity study, both methods present a determination coefficient of 0.999 at zinc concentrations between 10-500 μg/dl. However the percentages of recovery in that range are better with the 5-Br-PAPS based kit. A significant positive correlation was observed between zinc and citrate (r=0.724, P<0.001). Conclusion: Colorimetric methods are a good alternative to atomic absorption spectrophotometry, the colorimetric method based in 5-Br-PAPS showing better performance (AU)