scholarly journals Conditioning Efron’s biased coin design to ensure final balance

2021 ◽  
Vol 15 (2) ◽  
Author(s):  
Victoria P. Johnson
Keyword(s):  
Biased Coin Design ◽  
Biased Coin

scholarly journals The minimum effective concentration (MEC90) of ropivacaine for ultrasound-guided caudal block in anorectal surgery. A dose finding study

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257283
Author(s):  
Xuehan Li ◽  
Jun Li ◽  
Pei Zhang ◽  
Huifei Deng ◽  
Mingan Yang ◽  
...  
Keyword(s):  
Effective Concentration ◽  
Dose Finding ◽  
Anorectal Surgery ◽  
Sensory Blockade ◽  
Minimum Effective Concentration ◽  
Female Patients ◽  
Biased Coin Design ◽  
Finding Study ◽  
Dose Finding Study ◽  
Biased Coin

Background Caudal epidural block (CEB) provides reliable anesthesia for adults undergoing anorectal surgery. Despite the widely utilization, the minimum effective concentration for 90% patients (MEC90) of ropivacaine for CEB remains unknown. Objective To estimate MEC of ropivacaine for CEB in anorectal surgery. Design A prospective dose-finding study using biased coin design up-and-down sequential method. Setting Operating room and postoperative recovery area of Chengdu Shangjin Nanfu Hospital, from October 2019 to January 2020. Patients 50 males and 51 females scheduled for anorectal surgery. Interventions We conducted two independent biased coin design up-and down trials by genders. The concentration of ropivacaine administered to the first patient of male and female were 0.25% with fixed volume of 14ml for male and 12ml for female patients based on our previous study. In case of failure, the concentration was increased by 0.05% in the next subject. Otherwise, the next subject was randomized to a concentration 0.05% less with a probability of 0.11, or the same concentration with a probability of 0.89. Success was defined as complete sensory blockade of perineal area 15 min after the block evidenced by the presence of a lax anal sphincter and pain-free surgery. Main outcome measures The MEC of ropivacaine to achieve a successful CEB in 90%(MEC90) of the patients. Results The MEC90 of ropivacaine for CEB were estimated to be 0.35% (95% CI 0.29 to 0.4%) for male and 0.353% (95%CI 0.22 to 0.4%) for female. By extrapolation to MEC in 99% of subjects (MEC99) and pooled adjacent violators algorithm (PAVA) adjusted responses, it would be optimal to choose 0.4% ropivacaine with a volume of 14ml for male and 12ml for female. Conclusions A concentration of 0.35% ropivacaine with a volume of 14ml provided a successful CEB in 90% of the male patients, while 0.353% ropivacaine with a volume of 12ml provided a successful CEB in 90% of the female patients. A concentration of 0.4% and a volume of 14ml for male and 12 ml for female would be successful in 99% of the patients. Trial registration Chictr.org.cn identifier: No. ChiCTR 1900024315.

Generalized Efron's biased coin design and its theoretical properties

2016 ◽  
Vol 53 (2) ◽  
pp. 327-340 ◽  
Author(s):  
Yanqing Hu
Keyword(s):  
Clinical Trials ◽  
General Theory ◽  
Convergence Rate ◽  
Biased Coin Design ◽  
Target Ratio ◽  
Allocation Ratio ◽  
Target Allocation ◽  
Biased Coin

Abstract In clinical trials with two treatment arms, Efron's biased coin design, Efron (1971), sequentially assigns a patient to the underrepresented arm with probability p > ½. Under this design the proportion of patients in any arm converges to ½, and the convergence rate is n-1, as opposed to n-½ under some other popular designs. The generalization of Efron's design to K ≥ 2 arms and an unequal target allocation ratio (q1, . . ., qK) can be found in some papers, most of which determine the allocation probabilities ps in a heuristic way. Nonetheless, it has been noted that by using inappropriate ps, the proportion of patients in the K arms never converges to the target ratio. We develop a general theory to answer the question of what allocation probabilities ensure that the realized proportions under a generalized design still converge to the target ratio (q1, . . ., qK) with rate n-1.

Which design is better? Ehrenfest urn versus biased coin

2000 ◽  
Vol 32 (03) ◽  
pp. 738-749 ◽  
Author(s):  
Yung-Pin Chen
Keyword(s):  
Clinical Trial ◽  
Statistical Inferences ◽  
Biased Coin Design ◽  
Biased Coin

Two features are desired in designing a sequential clinical trial: randomness and balance. The former makes the ground for valid statistical inferences and the latter strengthens efficiency in inference procedures. Unfortunately randomness and balance can be in conflict with one another, and clinicians may be caught between the need for both of them. This paper raises an interesting question: can one design consistently achieve more balance than another when both designs own the same randomness? The Ehrenfest urn design is presented to allocate two treatments under a sequential clinical trial, and its balance and randomness properties are investigated. The design is compared with the biased coin design with imbalance tolerance.

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