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Children (Basel, Switzerland) Nov 2020Observational studies from large datasets are becoming more common in neonatology. In this review, we highlight the importance of the denominator in study design and... (Review)
Review
Observational studies from large datasets are becoming more common in neonatology. In this review, we highlight the importance of the denominator in study design and interpretation including examples of bias from source data, weight-based categories, age-related bias, and diagnosis-based denominators.
PubMed: 33171732
DOI: 10.3390/children7110216 -
Plastic and Reconstructive Surgery Nov 2021
Topics: Anatomy, Artistic; Human Body; Humans
PubMed: 34699489
DOI: 10.1097/01.prs.0000794844.50847.b1 -
JAMA Dermatology Jun 2018
PubMed: 29898222
DOI: 10.1001/jamadermatol.2018.2035 -
Scandinavian Journal of Primary Health... 1983
Topics: Family Practice; Health Planning; Humans; Population
PubMed: 6545030
DOI: 10.3109/02813438309034933 -
Human Reproduction (Oxford, England) Dec 2016Which outcome measures are reported in RCTs for IVF? (Review)
Review
STUDY QUESTION
Which outcome measures are reported in RCTs for IVF?
SUMMARY ANSWER
Many combinations of numerator and denominator are in use, and are often employed in a manner that compromises the validity of the study.
WHAT IS KNOWN ALREADY
The choice of numerator and denominator governs the meaning, relevance and statistical integrity of a study's results. RCTs only provide reliable evidence when outcomes are assessed in the cohort of randomised participants, rather than in the subgroup of patients who completed treatment.
STUDY DESIGN, SIZE, DURATION
Review of outcome measures reported in 142 IVF RCTs published in 2013 or 2014.
PARTICIPANTS/MATERIALS, SETTING, METHODS
Trials were identified by searching the Cochrane Gynaecology and Fertility Specialised Register. English-language publications of RCTs reporting clinical or preclinical outcomes in peer-reviewed journals in the period 1 January 2013 to 31 December 2014 were eligible. Reported numerators and denominators were extracted. Where they were reported, we checked to see if live birth rates were calculated correctly using the entire randomised cohort or a later denominator.
MAIN RESULTS AND THE ROLE OF CHANCE
Over 800 combinations of numerator and denominator were identified (613 in no more than one study). No single outcome measure appeared in the majority of trials. Only 22 (43%) studies reporting live birth presented a calculation including all randomised participants or only excluding protocol violators. A variety of definitions were used for key clinical numerators: for example, a consensus regarding what should constitute an ongoing pregnancy does not appear to exist at present.
LIMITATIONS, REASONS FOR CAUTION
Several of the included articles may have been secondary publications. Our categorisation scheme was essentially arbitrary, so the frequencies we present should be interpreted with this in mind. The analysis of live birth denominators was post hoc.
WIDER IMPLICATIONS OF THE FINDINGS
There is massive diversity in numerator and denominator selection in IVF trials due to its multistage nature, and this causes methodological frailty in the evidence base. The twin spectres of outcome reporting bias and analysis of non-randomised comparisons do not appear to be widely recognised. Initiatives to standardise outcome reporting, such as requiring all effectiveness studies to report live birth or cumulative live birth, are welcome. However, there is a need to recognise that early outcomes of treatment, such as stimulation response or embryo quality, may be appropriate choices of primary outcome for early phase studies.
STUDY FUNDING/COMPETING INTERESTS
J.W. is funded by a Doctoral Research Fellowship from the National Institute for Health Research. The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health. J.W. also declares that publishing research is beneficial to his career. J.W. and A.V. are statistical editors, and M.S. is Information Specialist, for the Cochrane Gynaecology and Fertility Group, although the views expressed here are not necessarily those of the group. D.R.B. is funded by the NHS as Scientific Director of a clinical IVF service. The authors declare no other conflicts of interest.
Topics: Birth Rate; Female; Fertilization in Vitro; Humans; Live Birth; Outcome Assessment, Health Care; Ovulation Induction; Pregnancy; Pregnancy Rate; Research Design; Treatment Outcome
PubMed: 27664214
DOI: 10.1093/humrep/dew227 -
Journal of Clinical Sleep Medicine :... Feb 2016Inconsistency in operationally defining sleep efficiency (SE) creates confusion with regard to the conceptualization and use of the construct by researchers and... (Review)
Review
Inconsistency in operationally defining sleep efficiency (SE) creates confusion with regard to the conceptualization and use of the construct by researchers and clinicians. The source of the inconsistency is the denominator of the widely published operational definition of SE: ratio of total sleep time (TST) to time in bed (TIB) (multiplied by 100 to yield a percentage). When taken literally, TIB includes non-sleep-related activity (e.g., reading, texting, conversing with a partner, watching television) both prior to initiating sleep and after the final awakening. However, the construct of SE refers to TST compared to the amount of time spent attempting to initially fall asleep and sleep discontinuity. Non-sleep related activities in bed do not reflect that construct. Also, time out of bed during nighttime awakenings, a manifestation of sleep discontinuity, should be included in the SE denominator. Using TIB as the denominator can also create a methodological problem when SE is an outcome measure in sleep intervention research. It is proposed that research and practice would benefit by clarifying and adopting a consistent operational definition that more accurately captures the construct of SE. An alternate denominator, duration of the sleep episode (DSE), is suggested, where DSE = sleep onset latency (SOL) + TST + time awake after initial sleep onset but before the final awakening (WASO) + time attempting to sleep after final awakening (TASAFA). The proposed formula for SE would be: SE = TST / DSE (× 100). DSE can be easily calculated using standard sleep diary entries along with one item from the Expanded Consensus Sleep Diary. Implications for insomnia research and practice are discussed.
Topics: Humans; Sleep; Sleep Hygiene; Sleep Medicine Specialty; Time Factors
PubMed: 26194727
DOI: 10.5664/jcsm.5498 -
Epidemiology and Infection Jul 2022While incidence studies based on hospitalisation counts are commonly used for public health decision-making, no standard methodology to define hospitals' catchment... (Review)
Review
While incidence studies based on hospitalisation counts are commonly used for public health decision-making, no standard methodology to define hospitals' catchment population exists. We conducted a review of all published community-acquired pneumonia studies in England indexed in PubMed and assessed methods for determining denominators when calculating incidence in hospital-based surveillance studies. Denominators primarily were derived from census-based population estimates of local geographic boundaries and none attempted to determine denominators based on actual hospital access patterns in the community. We describe a new approach to accurately define population denominators based on historical patient healthcare utilisation data. This offers benefits over the more established methodologies which are dependent on assumptions regarding healthcare-seeking behaviour. Our new approach may be applicable to a wide range of health conditions and provides a framework to more accurately determine hospital catchment. This should increase the accuracy of disease incidence estimates based on hospitalised events, improving information available for public health decision making and service delivery planning.
Topics: Cohort Studies; England; Hospitalization; Hospitals; Humans; Incidence
PubMed: 35811424
DOI: 10.1017/S0950268822000917 -
Journal of the American College of... Sep 2021
Topics: Humans; Prevalence
PubMed: 34556327
DOI: 10.1016/j.jacc.2021.06.052 -
The Journal of Craniofacial Surgery Jun 2023Since it was proposed in this journal in 2001, the cranial vault asymmetry index (CVAI) has been an important parameter for assessing cranial shape. However, different...
Since it was proposed in this journal in 2001, the cranial vault asymmetry index (CVAI) has been an important parameter for assessing cranial shape. However, different publications currently use different variables in the denominator of the CVAI formula. We thus investigated the use of long and short diagonal lengths as variables in the denominator of the CVAI formula. We searched the databases of PubMed, Google Scholar, and Scopus for articles published between 2016 and 2022 that cited the original work article of CVAI. Articles were included if they were written in English and if the denominator of the CVAI formula was specified. For multiple articles by the same author, only the most recent article was included. In total, 30 articles were included; 10 articles used the longer diagonal length as the denominator and 20 articles used the shorter diagonal length. No uniform trend was observed by a country or journal of publication. Application of the CVAI formula using different denominators yielded interchangeable results, and the resulting values had only negligible differences clinically. However, it would be necessary to create a standard formula for using the CVAI as a parameter for reporting cranial shape assessments consistently.
Topics: Humans; Plagiocephaly, Nonsynostotic; Skull; Bibliometrics; Databases, Factual
PubMed: 36922383
DOI: 10.1097/SCS.0000000000009263 -
Proceedings of the National Academy of... Dec 2023The discovery of the fractional quantum Hall state (FQHS) in 1982 ushered a new era of research in many-body condensed matter physics. Among the numerous FQHSs, those...
The discovery of the fractional quantum Hall state (FQHS) in 1982 ushered a new era of research in many-body condensed matter physics. Among the numerous FQHSs, those observed at even-denominator Landau level filling factors are of particular interest as they may host quasiparticles obeying non-Abelian statistics and be of potential use in topological quantum computing. The even-denominator FQHSs, however, are scarce and have been observed predominantly in low-disorder two-dimensional (2D) systems when an excited electron Landau level is half filled. An example is the well-studied FQHS at filling factor [Formula: see text] 5/2 which is believed to be a Bardeen-Cooper-Schrieffer-type, paired state of flux-particle composite fermions (CFs). Here, we report the observation of even-denominator FQHSs at [Formula: see text] 3/10, 3/8, and 3/4 in the lowest Landau level of an ultrahigh-quality GaAs 2D hole system, evinced by deep minima in longitudinal resistance and developing quantized Hall plateaus. Quite remarkably, these states can be interpreted as even-denominator FQHSs of CFs, emerging from pairing of higher-order CFs when a CF Landau level, rather than an electron or a hole Landau level, is half-filled. Our results affirm enhanced interaction between CFs in a hole system with significant Landau level mixing and, more generally, the pairing of CFs as a valid mechanism for even-denominator FQHSs, and suggest the realization of FQHSs with non-Abelian anyons.
PubMed: 38113254
DOI: 10.1073/pnas.2314212120