RESUMEN
BACKGROUND: In real-time PCR, it is necessary to consider the efficiency of amplification (EA) of amplicons in order to determine initial target levels properly. EAs can be deduced from standard curves, but these involve extra effort and cost and may yield invalid EAs. Alternatively, EA can be extracted from individual fluorescence curves. Unfortunately, this is not reliable enough. RESULTS: Here we introduce simultaneous non-linear fitting to determine - without standard curves - an optimal common EA for all samples of a group. In order to adjust EA as a function of target fluorescence, and still to describe fluorescence as a function of cycle number, we use an iterative algorithm that increases fluorescence cycle by cycle and thus simulates the PCR process. A Gauss peak function is used to model the decrease of EA with increasing amplicon accumulation. Our approach was validated experimentally with hydrolysis probe or SYBR green detection with dilution series of 5 different targets. It performed distinctly better in terms of accuracy than standard curve, DART-PCR, and LinRegPCR approaches. Based on reliable EAs, it was possible to detect that for some amplicons, extraordinary fluorescence (EA > 2.00) was generated with locked nucleic acid hydrolysis probes, but not with SYBR green. CONCLUSION: In comparison to previously reported approaches that are based on the separate analysis of each curve and on modelling EA as a function of cycle number, our approach yields more accurate and precise estimates of relative initial target levels.
Asunto(s)
Algoritmos , ADN/genética , Interpretación Estadística de Datos , Marcación de Gen/métodos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , Espectrometría de Fluorescencia/métodos , Distribución Normal , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
OBJECTIVE: In the past, our group took the position that we would not provide multifetal pregnancy reduction to a singleton regardless of starting number except for serious maternal medical indications or as a selective termination for diagnosed fetal anomalies. With evidence of increased safety and more women (many aged 40 years or more) asking for counseling about reduction to a singleton, we reviewed our prior reasoning. METHODS: We compared outcomes of 52 first-trimester twin-to-singleton for multifetal pregnancy reduction cases performed by a single operator to twin and singleton data from recent national register studies. RESULTS: Twin-to-singleton reductions represent less than 3% of all cases. Forty of 52 patients were aged 35 years or more, 19 were aged more than 40 years, and 2 were aged more than 50 years (age range 32-54 years). Since 1999, 23 of 28 had chorionic villus sampling before multifetal pregnancy reduction. Fifty-one of 52 reached viability with mean gestational age at delivery of 37.2 weeks. One of 52 patients miscarried (1.9%). Compared with multiple sources of data for twins, the loss rate is lower in twins reduced to a singleton. CONCLUSION: Until recently, multifetal pregnancy reductions to a singleton were rare. Physicians were concerned about the unknown risks of multifetal pregnancy reduction in this situation. They also had moral doubts about the justification to go "below twins." However, physicians know that spontaneous twin pregnancy losses average 8-10%. Also, with experience, multifetal pregnancy reduction has become very safe in our hands. Our data suggest that the likelihood of taking home a baby is higher after reduction than remaining with twins. We propose that twin-to-singleton reductions might be considered with appropriate constraints and safeguards.
Asunto(s)
Reducción de Embarazo Multifetal , Gemelos , Aborto Espontáneo , Adulto , Muestra de la Vellosidad Coriónica , Femenino , Humanos , Edad Materna , Persona de Mediana Edad , Embarazo , Reducción de Embarazo Multifetal/estadística & datos numéricos , Primer Trimestre del Embarazo , Embarazo de Alto RiesgoRESUMEN
OBJECTIVE: Multifetal pregnancy as a result of ovulation induction (OI) and assisted reproductive technologies (ART) correlate with Board certification in reproductive endocrinology and infertility (REI). DESIGN: Retrospective chart analysis of 304 patients referred to Wayne State University (WSU) and Thomas Jefferson University (TJU) for multifetal pregnancy reduction (MFPR) from March 1986 to January 1995 compared to 275 patients referred from January 1 to December 31, 2000 at MCP Hahnemann University. MATERIAL AND METHODS: Chart review for fetal number, pregnancy generation (OI or ART) and physician REI Board certification from the American Board of Specialties Obstetrics and Gynecology. Information was available on 296 of 304 patients studied in the 1986-1995 WSU cohort and 275 patients studied from the MCP Hahnemann 2000 cohort. RESULTS: Analysis of 296 multifetal pregnancies at WSU and TJU for REI Board status showed non-REI Board-certified (NREI) physicians generated 174 pregnancies with quadruplets or more compared to 122 quadruplets or more by REI Board-certified physicians. Board certification did not impact quadruplet or more rates for OI or ART (p < 0.368). Of 275 patients with triplets or more at MCP Hahnemann, 156 (56.7%) were from ARTs versus 41.2% from 1986-1995 (chi(2) = 13.1, p < 0.001). Quintuplets or more decreased from 18.5 to 9.7% (chi(2) = 8.3, p = 0.004), and for REIs from 22.1 to 9.6% (chi(2) = 4.7, p < 0.01), while 14.4% of cases coming from non-REIs had quintuplets versus 9.6% from REIs (p = NS). CONCLUSIONS: Cases of MFPR from ARTs have risen, while percentage of cases with quintuplets have fallen in half. We found no difference in quintuplets between REIs and non-REIs overall, but REI quintuplets fell significantly, and NREI has not.