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At least 397 records · Page 22Linked to original sources
PubMed2006

Can dissenting findings regarding the comparative effectiveness of ICSI and IVF be explained by a learning curve?

PURPOSE: To determine whether between-trial heterogeneity in relative risk of fertilisation for intracytoplasmic sperm injection (ICSI) compared to in vitro fertilisation (IVF) can be explained by learning or by between-trial variation in patient characteristics. METHODS: Systematic review and meta-analysis of trials comparing fertilisation outcomes for ICSI and IVF (without surgical sperm retrieval). Meta-regressions to identify associations between treatment effect and trial characteristics. RESULTS: Coefficients on individually significant covariates from the meta-regressions confirm that the ICSI versus IVF treatment effect is increased when patients are "unsuited for IVF" but reduced as semen quality improves and when IVF insemination concentrations are increased. However, the relative risk of fertilisation varies inversely with publication date; contrary to the hypothesised learning effect. CONCLUSION: While it is recognised that publication date might proxy for unobserved covariates, the possibility of a learning effect in favour of ICSI is not supported by the meta-regression.

Female↗
PubMed2006

The deep inferior epigastric perforator flap for breast reconstruction, the learning curve explored.

The deep inferior epigastric perforator (DIEP) flap has been used as the principle tool for secondary breast reconstruction in our department. This article details our experience in learning and improving the technique with the help of an external team of experienced surgeons. In our initial 65 DIEP flap breast reconstructions our total flap loss rate was reduced from 9.5 to 0%, partial flap loss rate from 31 to 0%, and fat necrosis rate from 17 to 4.3%. We illustrate how a surgical team, which might initially have considered the complication rate from DIEP flap breast reconstruction too high, can benefit from a staged approach to this complex, but useful, reconstruction technique.

Anastomosis, Surgical↗
PubMed2002

The learning curve for coil embolization of unruptured intracranial aneurysms.

BACKGROUND AND PURPOSE: Several studies have shown that procedural outcomes are better at high-volume institutions, possibly due to greater physician experience (learning) or practice (repetition). Our purpose was to determine whether outcomes for coil embolization improved with the experience of the practitioner, after adjusting for the perceived risk of treatment. METHODS: We identified all unruptured aneurysms treated with coil embolization at our institution from 1990 through 1997. A clinical nurse specialist abstracted the characteristics from cases that met the entry criteria. Two neurologists independently determined the complications by using definitions established a priori. The influence of experience of the treating-physician on complications was evaluated with univariate and multivariable logistic regression analyses. RESULTS: Sixteen complications occurred in 94 patients (17%) treated with coil embolization. Complications occurred in 53% of the first five cases that each of three physicians treated, and in 10% of later cases (P <.001). After an adjustment for all other predictors, including physician assessment of the risk of the procedure, the odds of a complication decreased with increasing physician experience (odds ratio, 0.69 for every five cases treated; 95% confidence interval: 0.50, 0.96; P=.03). CONCLUSION: The risk of complications with coil embolization of unruptured aneurysms appears to decrease dramatically with physician experience. Because the physicians in this study were highly experienced in other endovascular techniques at study onset, the rate of learning may not be generalizable to other centers.

Aged↗
PubMed1989

Freehand homograft aortic valve replacement--the learning curve: a technical analysis of the first 31 patients.

The technique for implanting the homograft aortic valve is significantly more complex than that of either the bioprosthetic or mechanical valve. During development of the procedure, errors of technique were committed; a critical analysis of the learning experience is presented. In the initial 31 patients, the following problems were encountered: mitral stenosis secondary to inadequate debulking of the homograft (1 patient), prolapse of a single homograft leaflet necessitating valve replacement three days later (1 patient), incorrect homograft orientation with torsion in a calcified aorta necessitating subsequent replacement (1 patient), and aortic sinus perforation (thawing injury) (1 patient). In addition, another 4 patients had diastolic murmurs thought to be secondary to inadequate tension setting of the homograft commissural posts. From this experience, several important technical considerations for homograft replacement of the aortic valve were noted: use of interrupted subannular sutures; careful inspection for aortic perforation (thawing); extensive trimming of the homograft septum and mitral remnant; orientation of the homograft to the recipient aorta to obtain the best commissural and sinus alignment; selection of another type of valve if the size of the recipient annulus is greater than 27 mm; retention of the homograft sinus, which orients to the recipient non-coronary sinus (for a calcified aorta); and exaggerated tension on the homograft commissural posts before initiation of the second suture line. There has been 1 hospital death and no late deaths. Adherence to rigid principles of technique has resulted in no further valve replacements and no incidences of valvular leakage at early or late follow-up.

Aortic Valve↗
PubMedDate not supplied

[The statistical evaluation of the reliability of learning curve differences].

A nonparametric method of statistical analysis of two related binary sequences of "1" and "0" is presented. This technique enables comparison between the dynamics of probability of appearance of 1" in the two sequences. This test can be applied to the problem of statistical comparison between the dynamics of learning of a "stimulus-reaction" type when the appearance of reaction to the stimulus is labeled as "1" and its absence as "0". The graphical interpretation is given and IBM-PC/AT program is characterized which realizes the advanced method.

Animals↗
PubMed2006

Ascending the learning curve--MSI testing experience of a six-laboratory consortium.

According to recently published guidelines, microsatellite instability (MSI) testing of colorectal cancers may be clinically indicated on a significant proportion of all colorectal tumors. To date, nothing has been published regarding the reproducibility of MSI testing between laboratories. We present MSI quality control activities experience of a six center multinational consortium, as laboratories developed competency with MSI testing and interpretation. The aim of this paper is to share lessons learned and to describe the final concordance rates in scoring MSI markers within this consortium.

Colorectal Neoplasms, Hereditary Nonpolyposis↗
PubMed1996

A numerical study on learning curves in stochastic multilayer feedforward networks.

The universal asymptotic scaling laws proposed by Amari et al. are studied in large scale simulations using a CM5. Small stochastic multilayer feedforward networks trained with backpropagation are investigated. In the range of a large number of training patterns t, the asymptotic generalization error scales as 1/t as predicted. For a medium range t a faster 1/t2 scaling is observed. This effect is explained by using higher order corrections of the likelihood expansion. It is shown for small t that the scaling law changes drastically, when the network undergoes a transition from strong overfitting to effective learning.

Learning↗
PubMed1992

Advantage of a smaller caliber fiberscope and learning curve on transurethral lithotripsy.

Transurethral lithotripsy was performed in 63 patients with ureteral calculi between September 1987 and March 1991. Three types of flexible nephroureteroscopes with diameters of 12.8F, 10.5F and 9.3F were used in groups 1, 2 and 3, respectively. The rate of successful stone disintegration and the stone-free rate 3 months after lithotripsy were 73% (11 of 15 patients) and 67% (10 of 15), respectively, in group 1, 93% (26 of 28) and 82% (23 of 28), respectively, in group 2, and 95% (19 of 20) and 85% (17 of 20), respectively, in group 3. Four complications were encountered in the patients treated with the 12.8F device (group 1). Our results clearly show that use of a slimmer fiberscope and the effect of learning to perform techniques with the flexible nephroureteroscope improved the success rate and decreased the complication rate in transurethral lithotripsy.

Adult↗
PubMedDate not supplied

Cholangiography during laparoscopic cholecystectomy--cumulative sum analysis of an institutional learning curve.

The ability to perform intraoperative cholangiography during laparoscopic cholecystectomy is an essential skill for the laparoscopic biliary surgeon. The volume of experience required to be able to consistently obtain a cholangiogram during laparoscopic cholecystectomy has not been determined. Cumulative sum analysis is a statistical technique which generates a graphical display that identifies periods of performance that fall below a predetermined standard for a given task. The cumulative sum (S(n)) for a series of observations is defined as: S(n)= summation operatorX(I) - X(o), where X(I) = 0 for a success, X(I) = 1 for a failure, and X(o) is the acceptable failure rate for the process under study. This function is plotted against the number of observations to create a curve. When the curve has a positive slope, the acceptable failure rate is being exceeded. When it reaches a plateau, the observed failure rate is equal to the acceptable failure rate. When the curve has a negative slope, the observed failure rate is lower than the acceptable failure rate. We performed a cumulative sum analysis of the first 97 intraoperative cholangiograms attempted during lap-aroscopic cholecystectomy at our institution. The results demonstrated that 46 cases were required to reach a level of proficiency where a cholangiogram could be obtained in 95% of attempts. Success rates of 85% and 90% were achieved at 16 and 25 cases, respectively. This form of analysis is a useful tool for estimating the number of attempts required to achieve a desired success rate when learning new procedures.

Adult↗