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Study Design
Published in Marcello Pagano, Kimberlee Gauvreau, Heather Mattie, Principles of Biostatistics, 2022
Marcello Pagano, Kimberlee Gauvreau, Heather Mattie
Ideally, randomization is carried out by an individual who is not involved in either the treatment of study subjects or in the assessment of outcomes. This is known as allocation concealment. Allocation concealment guarantees that the implementation of the randomization process is free from manipulation or bias. Traditionally, allocation concealment relied on sequentially numbered, sealed, opaque envelopes containing the randomization results. Today it is more common to use computer applications where investigators can access treatment assignments as subjects are enrolled.
Academic Viva
Published in Tjun Tang, Elizabeth O'Riordan, Stewart Walsh, Cracking the Intercollegiate General Surgery FRCS Viva, 2020
Allocation concealment is the method used to prevent clinicians working out the trial allocation of the next participant, thus influencing their decision as to whether or not to recruit the next eligible patient.
Clinical Trials
Published in Abhaya Indrayan, Research Methods for Medical Graduates, 2019
Rigid coding systems such as code A for the treatment and code B for the placebo should be avoided because breaking the code for one patient breaks it for the rest of trial. Allocation concealment is the procedure to ensure that the person allocating the treatment in a clinical trial is not able to guess what treatment the next person is going to get. The allocation of the subject to the treatments under trial is generally done with the help of opaque sealed envelopes that contain the allocation. They are opened only after the subject’s name and other identification have been written on the envelope so that the treatment cannot be changed. Concealment means that the envelopes are in random sequence and the serial on the envelope is not able to reveal what treatment it contains. A third party keeps all the records of the random sequence. This prevents bias of the allocating person in choosing which subject gets which treatment. Using a pharmacy as the third party is common for concealment of allocation in the case of drug trials. Concealment operationalizes the blinding and states how this was implemented. The details of this should be given in the protocol itself.
Could hyperbaric oxygen be an effective therapy option for pathological scars? A systematic review and meta-analysis
Published in Journal of Plastic Surgery and Hand Surgery, 2023
Ruxin Xie, Ai Zhong, Junliang Wu, Ying Cen, Junjie Chen
The Cochrane Collaboration tool [16] was used to help assess the risk of bias in the included studies: (1) Random sequence generation (selection bias). How were the participants randomized to groups? (2) Allocation concealment (selection bias). Was the group allocation of participants unknown to the recruiting trialist? (3) Blinding (performance and detection bias). Was a reliable method of blinding therapy employed? (4) Blinding of participants and personnel (performance bias). Can we be confident participants and trial personnel were unaware of allocation? (5) Blinding of outcome assessors (detection bias). Were those measuring outcomes unaware of allocation? (6) Incomplete outcome data (attrition bias). Were missing data a potential source of bias? (7) Selective reporting (reporting bias). Were planned outcomes missing in the trial report?
Efficacy and safety of nafamostat mesilate anticoagulation in blood purification treatment of critically ill patients: a systematic review and meta-analysis
Published in Renal Failure, 2022
Yao Lin, Yiming Shao, Yuchun Liu, Ruoxuan Yang, Shuanglin Liao, Shuai Yang, Mingwei Xu, Junbing He
The methodological quality of the 4 enrolled randomized controlled trials is presented in Figure 2, and none of the studies described allocation concealment. Because the two interventions were significantly different, blinding of participants and personnel was not practical, but lack of blinding did not produce significant bias; thus this domain was not considered for the study-level assessment. Blinding of outcome assessment was not performed in two studies [27,29], and insufficient information was available to permit judgment of another two studies [17,28]. One study [28] was supported by an NM manufacturer (SK Chemical); therefore, the other biases were unclear. Two studies [17,28] had a high risk of incomplete outcomes since more than 10% of patients in these two studies dropped out after allocation. We considered all four RCTs to be at high risk of bias in one or more criteria and rated them as of 'poor overall quality’. In addition, none of the cohort studies fulfilled all quality indicators, and the quality assessment scores ranged from 4 to 10 (out of a possible score of 14; Additional File 3). The most common methodological limitations that existed in the enrolled studies were the lack of blinding of outcome assessors [30,32–36], sample size justification [30–36] and different levels of exposure as related to the outcome [30,32–36].
A meta-analysis of the effect of the Early Start Denver Model in children with autism spectrum disorder
Published in International Journal of Developmental Disabilities, 2022
Zhi Wang, Sau Cheong Loh, Jing Tian, Qian Jiang Chen
In addition, we used the Cochrane risk of bias assessment tool based on seven methodological quality indicators. Random sequence generation indicates selection bias (i.e. biased allocation to interventions) due to inadequate generation of a randomized sequence. Allocation concealment also signifies selection bias owing to the inadequate protection of allocations prior to the assignment. Blinding of participants and personnel refers to performance bias, which results from participants’ and personnel’s knowledge of the allocated interventions. Blinding of outcome assessment implies a detection bias as a result of the outcome assessors’ knowledge of the allocated interventions. Incomplete outcome data denote attrition bias, which results from the amount, nature, or management of incomplete outcome data. Selective reporting indicates reporting bias due to the presentation of specific results. Other bias specifies includes bias associated with problems not covered elsewhere in the table. According to the Cochrane evaluation criteria, the fulfilment of the quality criteria by four or more items denotes the existence of low-risk bias. Additionally, the fulfilment attainment of the quality criteria by two or more items indicates medium-risk bias. However, if only one item meets the quality criteria, it implies the presence of high-risk bias (Higgins et al. 2019).