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Single-level analysis of intervention studies with hierarchically structured data: a cautionary note.

R L Brown·L J Baumann·L Cameron
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BiasHumansModels, StatisticalMonte Carlo MethodPrimary Health CareComparative StudyJournal ArticleResearch Support, Non-U.S. Gov't

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R L Brown, L J Baumann, L Cameron. Single-level analysis of intervention studies with hierarchically structured data: a cautionary note.. https://doi.org/10.1097/00006199-199611000-00012

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Assessment of blinding in pharmacotherapy and noninvasive neuromodulation randomized controlled trials for neuropathic pain in adults.

In randomized controlled trials (RCTs), study participants and research personnel are often blinded to minimize biases related to knowing treatment allocation. To determine if blinding was effective, participants may be asked which treatment they believe they received ("treatment guess"). This descriptive review characterized blinding assessment (BA) reporting in pharmacotherapy and neuromodulation neuropathic pain RCTs. Of 288 papers, 36 (12.5%) reported a BA. One paper reported the results of 2 studies, so in total 37 studies with a BA were assessed. Of these, 19 were crossover, 17 parallel, and 1 partial crossover in design. All 37 studies assessed participant blinding, and 10 also assessed investigator blinding. Approximately 27% included an "unsure" answer option for treatment guess, and 38% asked the reason for the guess. There were no clear patterns in BA reporting across time nor based on treatment type. Seventeen trials provided sufficient data to calculate Bang Blinding Index (BI) to determine blinding success. Participants remained blinded (BI = 0 &#xb1; 0.2) in 10/17 placebo and 10/17 treatment arms, 6 placebo and 5 treatment arms had a BI > 0.2 suggesting possible unblinding, whereas 1 placebo and 2 treatment arms had a BI < -0.2 suggesting misinformed guessing. Overall, we found that BAs are done in a minority of published neuropathic pain trials and with variable methodology. Given the importance of minimizing risk of bias because of treatment unblinding, future studies should consider including BAs, and further consensus building is necessary to determine if and how BAs should be conducted and interpreted in analgesic clinical trials.

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PubMed2004

Effects of duplicate and screening isolates on surveillance of community and hospital antibiotic resistance.

OBJECTIVES: To investigate common contentions that duplicate and screening isolates consistently show marked excess resistance, and that inclusion of such isolates significantly distorts regional resistance estimates. METHODS: Two Welsh surveys of antibiotic resistance for routine diagnostic isolates were analysed, comprising 309,129 isolates of six common community pathogens and 85,061 ward isolates of 11 common hospital pathogens. Duplicate isolates were defined as isolates from the same patient of the same pathogen with an indistinguishable susceptibility pattern, excluding the initial isolate. Significance was assessed from 95% confidence limits of the difference between resistance estimates. RESULTS: Duplicate isolates comprised approximately 20% of total isolates. For the 195 antibiotic-pathogen combinations investigated, differences in resistance between duplicate and non-duplicate isolates were statistically significant for 93. Only 54 combinations showed significantly increased resistance amongst duplicates, and only 30 of these showed a difference >5%. Comparisons of de-duplicated with un-de-duplicated regional resistance estimates showed significant differences for only 18 of 195 antibiotic-pathogen combinations; none were sufficient to alter judgement on clinical use. Screening isolates produced little disturbance of resistance estimates for Staphylococcus aureus, with the exception of flucloxacillin resistance, where inclusion of screening and duplicate isolates resulted in an increase of 4.4% for both community and hospital resistance estimates. CONCLUSIONS: The contentions were incorrect for these regional surveys. However, the proportion (and so effects) of screening and duplicate isolates may be greater in surveys of units with frequent repetitive sampling practice (burns, ITU, cystic fibrosis), or pathogens subjected to unusually intensive infection control sampling.

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