Specific GAG ratios in the diagnosis of mucopolysaccharidoses

Mucopolysaccharidoses (MPS) screening is tedious and still performed by analysis of total glycosaminoglycans (GAG) using 1,9-dimethylmethylene blue (DMB) photometric assay, although false positive and negative tests have been reported. Analysis of differentiated GAGs have been pursued classically by gel electrophoresis or more recently by quantitative LC-MS assays. Secondary elevations of GAGs have been reported in urinary tract infections (UTI). In this manuscript, we describe the diagnostic accuracy of urinary GAG measurements by LC-MS for MPS typing in 68 untreated MPS and mucolipidosis (ML) patients, 183 controls and 153 UTI samples. We report age-dependent reference values and cut-offs for chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS) and keratan sulfate (KS) and specific GAG ratios. The use of HS/DS ratio in combination to GAG concentrations normalized to creatinine improves the diagnostic accuracy in MPS type I, II, VI and VII. In total 15 samples classified to the wrong MPS type could be correctly assigned using HS/DS ratio. Increased KS/HS ratio in addition to increased KS improves discrimination of MPS type IV by excluding false positives. Some samples of UTI patients showed elevation of specific GAGs, mainly CS, KS and KS/HS ratio and could be misclassified as MPS type IV. Finally, DMB photometric assay performed in MPS and ML samples reveal four false negative tests (sensitivity of 94%). In conclusion, specific GAG ratios in complement to quantitative GAG values obtained by LC-MS enhance discrimination of MPS types. Exclusion of patients with UTI improve diagnostic accuracy in MPS IV but not in other types.

The fallacy of global comparisons based on per capita measures

Media, social scientists and public health researchers often present comparisons across countries, and policy makers use such comparisons to take evidence-based action. For a meaningful comparison among countries, one often needs to normalize the measure for differences in population size. To address this issue, the first choice is usually to calculate per capita ratios. Such ratios, however, normalize the measure for differences in population size directly only under the highly restrictive assumption of a proportional increase of the measure with population size. Violation of this assumption frequently leads to misleading conclusions. We compare per capita ratios with an approach based on regression, a widely used statistical procedure that eliminates many of the problems with ratios and allows for straightforward data interpretation. It turns out that the per capita measures in three global datasets (gross domestic product, COVID-19-related mortality and CO2 production) systematically overestimate values in countries with small populations, while countries with large populations tend to have misleadingly low per capita ratios owing to the large denominators. Unfortunately, despite their biases, comparisons based on per capita ratios are still ubiquitous, and they are used for influential recommendations by various global institutions. Their continued use can cause significant damage when employed as evidence for policy actions and should therefore be replaced by a more scientifically substantiated and informative method, such as a regression-based approach.

Nurse/midwife-to-patient ratios: A scoping review

BACKGROUND

A significant body of work has linked high nurse or midwife workload to negative patient outcomes. Anecdotal reports suggest that mandated ratio models enhance patient care and improve nurse job satisfaction. However, there is limited focused research.

OBJECTIVE

To identify key outcomes, implementation processes, and research needs regarding nurse/midwife-to-patient ratios in the Australian healthcare context.

DESIGN

Scoping review.

METHODS

Data sources were CINAHL, Open Dissertations, Medline, and Scopus. 289 articles screened, and 53 full text documents independently assessed against criteria by two reviewers and conflicts resolved by a third reviewer, using Covidence™. Three studies were included in this review.

RESULTS

Studies focused on nurse (job satisfaction, burnout), patient (mortality, readmission, length of stay) and system (costs) outcomes with limited information on implementation processes and no midwifery research.

CONCLUSIONS

Ratios provide benefits for patients, nurses, and hospitals although there is limited research in Australia. Implementation was poorly reported..

The marginality principle revisited: Should "higher-order" terms always be accompanied by "lower-order" terms in regression analyses?

The marginality principle guides analysts to avoid omitting lower-order terms from models in which higher-order terms are included as covariates. Lower-order terms are viewed as "marginal" to higher-order terms. We consider how this principle applies to three cases: regression models that may include the ratio of two measured variables; polynomial transformations of a measured variable; and factorial arrangements of defined interventions. For each case, we show that which terms or transformations are considered to be lower-order, and therefore marginal, depends on the scale of measurement, which is frequently arbitrary. Understanding the implications of this point leads to an intuitive understanding of the curse of dimensionality. We conclude that the marginality principle may be useful to analysts in some specific cases but caution against invoking it as a context-free recipe.

Relative growth rate (RGR) and other confounded variables: mathematical problems and biological solutions

BACKGROUND

Relative growth rate (RGR) has a long history of use in biology. In its logged form, RGR = ln[(M + ΔM)/M], where M is size of the organism at the commencement of the study, and ΔM is new growth over time interval Δt. It illustrates the general problem of comparing non-independent (confounded) variables, e.g. (X + Y) vs. X. Thus, RGR depends on what starting M(X) is used even within the same growth phase. Equally, RGR lacks independence from its derived components, net assimilation rate (NAR) and leaf mass ratio (LMR), as RGR = NAR × LMR, so that they cannot legitimately be compared by standard regression or correlation analysis.

FINDINGS

The mathematical properties of RGR exemplify the general problem of 'spurious' correlations that compare expressions derived from various combinations of the same component terms X and Y. This is particularly acute when X >> Y, the variance of X or Y is large, or there is little range overlap of X and Y values among datasets being compared. Relationships (direction, curvilinearity) between such confounded variables are essentially predetermined and so should not be reported as if they are a finding of the study. Standardizing by M rather than time does not solve the problem. We propose the inherent growth rate (IGR), lnΔM/lnM, as a simple, robust alternative to RGR that is independent of M within the same growth phase.

CONCLUSIONS

Although the preferred alternative is to avoid the practice altogether, we discuss cases where comparing expressions with components in common may still have utility. These may provide insights if (1) the regression slope between pairs yields a new variable of biological interest, (2) the statistical significance of the relationship remains supported using suitable methods, such as our specially devised randomization test, or (3) multiple datasets are compared and found to be statistically different. Distinguishing true biological relationships from spurious ones, which arise from comparing non-independent expressions, is essential when dealing with derived variables associated with plant growth analyses.

Blood component ratios in children with non-traumatic life-threatening bleeding

BACKGROUND AND OBJECTIVES

In paediatric trauma patients, there are limited prospective data regarding blood components and mortality, with some literature suggesting decreased mortality with high ratios of plasma and platelets to red blood cells (RBCs) in massive transfusions; however, most paediatric massive transfusions occur for non-traumatic aetiologies and few studies assess blood product ratios in these children. This study's objective was to evaluate whether high blood product ratios or low deficits conferred a survival benefit in children with non-traumatic life-threatening bleeding.

MATERIALS AND METHODS

This is a secondary analysis of the five-year, multicentre, prospective, observational massive transfusion epidemiology and outcomes in children study of children with life-threatening bleeding from US, Canadian and Italian medical centres. Primary interventions were plasma:RBC and platelets:RBC (high ratio ≥1:2 ml/kg) and plasma and platelet deficits. The primary outcome was mortality at 6 h, 24 h and 28 days. Multivariate logistic regression models were used to determine independent associations with mortality.

RESULTS

A total of 222 children were included from 24 medical centres: 145 children (median [interquartile range] age 2.1 years [0.3-11.8]) with operative bleeding and 77 (8.0 years [1.2-14.7]) with medical bleeding. In adjusted analyses, neither blood product ratios nor deficits were associated with mortality at 6 h, 24 h or 28 days.

CONCLUSION

This paper addresses a lack of prospective data in children regarding optimal empiric massive transfusion strategies in non-traumatic massive haemorrhage and in finding no decrease in mortality with high plasma or platelet to RBC ratios or lower deficits supports an exploratory analysis for mortality.

Evaluation of simple laboratory parameters in SARS-CoV-2 infection: the role of ratios

BACKGROUND

The real predictive prognostic capacity of cellular indices (or ratios) is unclear in SARS-CoV-2 infection. This study aimed to assess the prognostic role of previously well-known laboratory indices and new ones in hospitalized COVID-19 patients.

METHODS

A retrospective observational study from March to May 2022 evaluated laboratory indices on admission (neutrophil to lymphocyte-, derived neutrophil to lymphocyte-, platelet to lymphocyte-, CRP to lymphocyte-, CRP to albumin-, fibrinogen to lymphocyte-, d-dimer to lymphocyte-, ferritin to lymphocyte-, LDH to lymphocyte-, and IL-6 to lymphocyte ratios), in patients hospitalized due to SARS-CoV2 infection to determine the association with mortality, admission to an intensive care unit (ICU), need for non-invasive mechanical ventilation (NIMV), orotracheal intubation (OTI), or combined event at 30 days follow-up.

RESULTS

A total of 1113 COVID-19 patients were evaluated with a mean age of 64.1 ± 15.9 years (58.49% male), 166 (14.91%) patients died, 58 (5.21%) required ICU admission, 73 (6.56%) needed NIMV, 46 (4.23%) needed OTI, and 247 (22.19%) presented the combined event. All the ratios evaluated in this study showed statistical significance in the univariate analysis for mortality and combined event; however, only d-dimer to lymphocyte ratio >0.6 presented an independent association in the multivariate analysis for 30-day mortality (adjusted OR 2.32; p = .047) and 30-day combined event (adjusted OR 2.62; p = .014).

CONCLUSIONS

Laboratory indices might be a potential biomarker for better prognosis stratification in hospitalized COVID-19 patients. d-Dimer to lymphocyte ratio presents an independent association for 30-day mortality and 30-day adverse outcomes in hospitalized COVID-19 patients.

Impact of School Nurse Ratios and Health Services on Selected Student Health and Education Outcomes: North Carolina, 2011-2016

BACKGROUND

Determination of adequate school nurse staffing is a complex process. School nurse-to-student ratios and the health services school nurses provide to students should be considered. The purpose of this study was to examine the impact of North Carolina school nurse-to-student ratios and school nurse health services on the health and education outcomes (eg, absences, grades, self-management) of students receiving services for asthma and diabetes.

METHODS

This study of all 115 school districts in North Carolina used the Annual School Health Services Report Survey from 2011 to 2016. Descriptive statistics for health services, programs and outcomes, and generalized linear modeling were used to estimate the association of ratios and health services with asthma and diabetes outcomes.

RESULTS

By the 2015-2016 school year, the average ratio decreased to 1:1086 in North Carolina public schools. Annually, 100,187 students received services for asthma, 3832 students received services for type 1 diabetes, and 913 students received services for type 2 diabetes. Lower ratios and nurse health services were associated with improved student outcomes, including decreased absences (p = .05), improved grades (p = .05), and student self-management of their health condition (p = .05).

CONCLUSIONS

Lower school nurse-to-student ratios and services were associated with improvements in students' health and education outcomes.

Ultrasound Characterization of Patellar Tendon in Non-Elite Sport Players with Painful Patellar Tendinopathy: Absolute Values or Relative Ratios? A Pilot Study

Imaging findings in patellar tendinopathy are questioned. The aim of this pilot study was to characterize ultrasound measures, by calculating ultrasound ratio and neovascularization of the patellar tendon in non-elite sport players with unilateral painful patellar tendinopathy. Cross-sectional area (CSA), width, and thickness of the patellar tendon were assessed bilaterally in 20 non-elite sport-players with unilateral painful patellar tendinopathy and 20 asymptomatic controls by a blinded assessor. Ultrasound ratios were calculated to discriminate between symptomatic and asymptomatic knees. The Ohberg score was used for characterizing neovascularization. We found that non-elite sport players with patellar tendinopathy exhibited bilateral increases in CSA, width, and thickness of the patellar tendon compared to asymptomatic controls (Cohen d > 2). The ability of ultrasound ratios to discriminate between painful and non-painful patellar tendons was excellent (receiver operating characteristic, ROC > 0.9). The best diagnostic value (sensitivity: 100% and specificity: 95%) was observed when a width ratio ≥ 1.29 between the symptomatic and asymptomatic patellar tendon was used as a cut-off. Further, neovascularization was also observed in 70% of non-elite sport players with unilateral patellar tendinopathy. A greater CSA ratio was associated with more related-disability and higher tendon neovascularization. This study reported that non-elite sport players with painful unilateral patellar tendinopathy showed structural ultrasound changes in the patellar tendon when compared with asymptomatic controls. Ultrasound ratios were able to discriminate between symptomatic and asymptomatic knees. Current results suggest that ultrasound ratios could be a useful imaging outcome for identifying changes in the patellar tendon in sport players with unilateral patellar tendinopathy.

Planning the supply of aged care services: It's time to talk denominators

OBJECTIVES

This paper explores how changes in demography, service use and the aged care system have implications for the appropriateness of the denominator in the aged care provision ratio.

METHODS

Official statistics were analysed to create five alternative scenarios for residential care planning in a 2000-2027 time series.

RESULTS

The four age-based denominators and a revised denominator incorporating age- and sex-specific disability rates generated diverse levels of absolute supply. The 75+ denominator produced 1400 fewer beds than the 70+ denominator by 2018, but over 14 000 additional beds by 2027.

CONCLUSION

The 70+ based ratio developed almost forty years ago has served its purpose reasonably well. However, changes in the nature of the aged care system, different patterns of use by age and sex, and demographic changes suggest that long-term aged care planning requires careful review in choosing a more robust version of the provision ratio for the future.

Platelet-to-lymphocyte and Neutrophil-to-lymphocyte Ratios Predict Target Vessel Restenosis after Infrainguinal Angioplasty with Stent Implantation

Platelet-to-lymphocyte (PLR), neutrophil-to-lymphocyte (NLR) and lymphocyte-to-monocyte (LMR) ratios are associated with the occurrence of critical limb ischemia in peripheral artery disease (PAD). We therefore investigated whether PLR, NLR or LMR are linked to target vessel restenosis (TVR) following infrainguinal angioplasty and stenting. Moreover, we studied on-treatment platelet reactivity and neutrophil-platelet aggregate (NPA) formation as potential underlying mechanisms. Platelet, neutrophil, lymphocyte and monocyte counts were determined one day after angioplasty and stenting in 95 stable PAD patients. Platelet reactivity and NPA formation in response to protease-activated receptor−1 stimulation were measured by light transmission aggregometry (LTA) and flow cytometry, respectively. PLR and NLR were significantly higher in patients who subsequently developed TVR (both p < 0.05). In contrast, LMR did not differ significantly between patients without and with TVR (p = 0.28). A PLR ≥ 91 and NLR ≥2.75 were identified as the best thresholds to predict TVR, providing sensitivities of 87.5% and 81.3%, and specificities of 34.9% and 50.8%, respectively, and were therefore defined as high PLR and high NLR. TVR occurred significantly more often in patients with high PLR and high NLR than in those with lower ratios (both p < 0.05). Patients with high PLR and high NLR exhibited significantly increased on-treatment platelet aggregation compared to those with lower ratios, and patients with high PLR had higher levels of NPA formation (all p < 0.01). In conclusion, PLR and NLR predict TVR after infrainguinal angioplasty with stent implantation. Platelet activation and neutrophil-platelet interaction may be involved in the underlying pathomechanisms

The Predictive Value of the Neutrophil-to-Lymphocyte and Platelet-to-Lymphocyte Ratio in Patients with Recurrent Idiopathic Granulomatous Mastitis

Objective

The aim of this study was to investigate the relationship between the inflammatory parameters including neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) and the prognosis of idiopathic granulomatous mastitis (IGM).

Materials and methods

In this retrospective study, a total of 41 patients with IGM who had no malignant disease or inflammatory pathologies were included between January 2010 and December 2017. The patients were divided into two groups according to presence or absence of recurrence. Subsequently, the relationship between patient characteristics, pre- and postoperative NLR and PLR levels and disease recurrence were evaluated.

Results

With a mean follow-up period of 28.4 months, 19.5% of patients were found to have recurrent IGM. Age, body mass index, patient characteristics such as oral contraceptive use, smoking status, and family history, surgical treatment and postoperative NLR, preoperative PLR, and postoperative PLR were not statistically significant between groups. However, only preoperative NLR was significantly associated with a recurrent IGM (p=0.024). Preoperative NLR predicted recurrence with a sensitivity of 62.5% and specificity of 84.8%.

Conclusion

These results demonstrated that a high level of NLR was predictive of poor outcome in patients with IGM.

Simultaneous confidence intervals for ratios with application to the gold standard design with more than one experimental treatment

Considering a study design with two experimental treatments, a reference treatment and a placebo, we extend a previous approach considering the ratios of effects to a procedure for analyzing multiple ratios. The technical framework for constructing tests and compatible simultaneous confidence intervals is set in a general manner. Besides a single step procedure and its extension to a stepdown procedure, also, an informative stepwise procedure in the spirit of our previous work is developed. The latter is especially interesting, because noninferiority studies require informative confidence intervals to infer more information than just noninferiority at the prespecified margin. Results from a simulation study for the three methods are shown. We also argue that an extension to more than two experimental treatments is straightforward.

Comparative Strength and Endurance Parameters of the Craniocervical and Cervicothoracic Extensors and Flexors in Females With and Without Idiopathic Neck Pain

Isometric strength and endurance performance of cervical flexor and extensor muscles were compared in women with (n = 30) and without (n = 30) idiopathic neck pain at the craniocervical and cervicothoracic axes. Strength and endurance time (time to task failure in seconds) at 50% maximal voluntary contraction were recorded in 4 directions (craniocervical flexion/extension and cervicothoracic flexion/extension) and 6 strength and endurance ratios were calculated. Participants in both groups were matched for body mass index. The idiopathic neck pain group demonstrated significantly less strength for the cervicothoracic flexors and extensors (1.58-4.7 N·m [12.4%-17.9%] less, P < .04) and significantly less endurance time for the cervicothoracic and craniocervical flexors (10.77-10.9 s [23.3%-27.5%] less, P < .03). The cervicothoracic extension to craniocervical flexion strength ratio was also lower in the idiopathic neck pain group (P = .01); however, no other strength or endurance ratio was significantly different between groups. This exploratory study suggests assessing specific performance parameters accounting for regional muscular differences in the upper and lower neck is potentially informative to understanding impairments in neck pain conditions, particularly as impairments may not be uniform across muscle groups.

Task Constraints Affect Mapping From Approximate Number System Estimates to Symbolic Numbers

The Approximate Number System (ANS) allows individuals to assess nonsymbolic numerical magnitudes (e.g., the number of apples on a tree) without counting. Several prominent theories posit that human understanding of symbolic numbers is based – at least in part – on mapping number symbols (e.g., 14) to their ANS-processed nonsymbolic analogs. Number-line estimation – where participants place numerical values on a bounded number-line – has become a key task used in research on this mapping. However, some research suggests that such number-line estimation tasks are actually proportion judgment tasks, as number-line estimation requires people to estimate the magnitude of the to-be-placed value, relative to set upper and lower endpoints, and thus do not so directly reflect magnitude representations. Here, we extend this work, assessing performance on nonsymbolic tasks that should more directly interface with the ANS. We compared adults’ (n = 31) performance when placing nonsymbolic numerosities (dot arrays) on number-lines to their performance with the same stimuli on two other tasks: Free estimation tasks where participants simply estimate the cardinality of dot arrays, and ratio estimation tasks where participants estimate the ratio instantiated by a pair of arrays. We found that performance on these tasks was quite different, with number-line and ratio estimation tasks failing to the show classic psychophysical error patterns of scalar variability seen in the free estimation task. We conclude the constraints of tasks using stimuli that access the ANS lead to considerably different mapping performance and that these differences must be accounted for when evaluating theories of numerical cognition. Additionally, participants showed typical underestimation patterns in the free estimation task, but were quite accurate on the ratio task. We discuss potential implications of these findings for theories regarding the mapping between ANS magnitudes and symbolic numbers.

Implementation of a model of emergency care in an Australian hospital

AIM

Emergency departments are characterised by a fast-paced, quick turnover and high acuity workload, therefore appropriate staffing is vital to ensure positive patient outcomes. Models of care are frameworks in which safe and effective patient-to-nurse ratios can be ensured. The aim of this study was to implement a supportive and transparent model of emergency nursing care that provides structure - regardless of nursing staff profile, business or other demands; improvement to nursing workloads; and promotes individual responsibility and accountability for patient care.

METHOD

A convergent parallel mixed-method approach was used. Quantitative data were analysed using descriptive statistics and the qualitative data used a thematic analysis to identify recurrent themes.

RESULTS

Data post-implementation of the model of emergency nursing care indicate improved staff satisfaction in relation to workload, patient care and support structures.

CONCLUSION

The development and implementation of a model of care in an emergency department improved staff workload and staff's perception of their ability to provide care.

Diagnostic Validity Comparison Between Criteria Based on CSF Alzheimer's Disease Biomarkers

AIM

To compare the diagnostic validity of NIA-AA criteria, for AD CSF biomarkers, with our own new criteria.

MATERIALS AND METHODS

Between 2008 and 2011, 170 patients with Mild Cognitive Impairment (MCI) were included. CSF levels of Aβ1-42, T-tau, P-tau181, and ratios of T-tau/Aβ1-42 and P-tau181/Aβ1-42 were analyzed. In our criteria, we considered 3 or more abnormal variables indicative of a high likelihood of MCI due to AD.

RESULTS

After a clinical follow-up of 4.5 ± 1.2 years, 44 patients remained stable, 95 developed AD, 15 other forms of dementia, 7 died and 9 received other diagnoses. Using the NIA-AA criteria and our own criteria, the diagnostic validity of the CSF biomarkers was 58% versus 85%, specificity 84% versus 72%, PPV 82% versus 79% and NPV 61% versus 79%.

CONCLUSION

The inclusion of the ratios in diagnostic criteria increases sensitivity and NPV for the diagnosis of MCI due to AD.

Differential Strength and Endurance Parameters of the Craniocervical and Cervicothoracic Extensors and Flexors in Healthy Individuals

This study examined isometric strength (maximal voluntary contraction [MVC]) and endurance of cervical flexor and extensor muscles in healthy individuals at the craniocervical (CC) and cervicothoracic (CT) axes. MVC and endurance measures (time to task failure in seconds [s]) at 50% MVC were recorded in 4 directions (CC flexion, CC extension, CT flexion, and CT extension) in 20 males and 20 females, and 6 strength and endurance ratios were calculated. The findings showed that the cervical extensor muscles are not only much stronger than the flexors (1.3-2 times greater MVC), but also have greater capacity for endurance (2-2.4 times greater). While males produced significantly greater MVC recordings than females (P < .003), strength ratios (P > .06) and endurance measures (P > .11) were similar. Endurance ratios were also similar except the CT extension to CC flexion ratio, which was significantly larger in females compared with males (P = .03). These findings demonstrate that substantial but normal variation exists in strength and endurance parameters between cervical flexor and extensor muscles. This is informative to clinicians when evaluating the performance of these neck muscles or when deciding on exercise parameters (eg, load, duration) when training their performance.

Comparison of bone regeneration in alveolar bone of dogs on mineralized collagen grafts with two composition ratios of nano-hydroxyapatite and collagen

To study the effect of two composition ratios of nano-hydroxyapatite and collagen (NHAC) composites on repairing alveolar bone defect of dogs. Eighteen healthy adult dogs were randomly divided into three groups. Two kinds of the NHAC composites were prepared according to the constituent ratios of 3:7 and 5:5; immediately after extraction of the mandibular second premolars, each kind of the NHAC composite was implanted into extraction socket, respectively: Group I, nHA/Col = 3:7; Group II, nHA/Col = 5:5 and Group III, blank control group. The bone-repairing ability of the two grafts was separately analyzed by morphometric measurement, X-ray tomography examination and biomechanical analysis at 1st, 3rd and 6th month post-surgical, respectively. The NHAC composites were absorbed gradually after implanting into alveolar bone defect and were replaced by new bone. The ratios of new bone formation of Group I was significantly higher than that of Group II after 3 months (P < 0.05). The structure and bioactive performance can be improved when the ratio between the collagen and the hydroxyapatite was reasonable, and the repairing ability and effect in extraction sockets are obviously better.

Multiple imputation for an incomplete covariate that is a ratio

We are concerned with multiple imputation of the ratio of two variables, which is to be used as a covariate in a regression analysis. If the numerator and denominator are not missing simultaneously, it seems sensible to make use of the observed variable in the imputation model. One such strategy is to impute missing values for the numerator and denominator, or the log-transformed numerator and denominator, and then calculate the ratio of interest; we call this ‘passive’ imputation. Alternatively, missing ratio values might be imputed directly, with or without the numerator and/or the denominator in the imputation model; we call this ‘active’ imputation. In two motivating datasets, one involving body mass index as a covariate and the other involving the ratio of total to high-density lipoprotein cholesterol, we assess the sensitivity of results to the choice of imputation model and, as an alternative, explore fully Bayesian joint models for the outcome and incomplete ratio. Fully Bayesian approaches using Winbugs were unusable in both datasets because of computational problems. In our first dataset, multiple imputation results are similar regardless of the imputation model; in the second, results are sensitive to the choice of imputation model. Sensitivity depends strongly on the coefficient of variation of the ratio's denominator. A simulation study demonstrates that passive imputation without transformation is risky because it can lead to downward bias when the coefficient of variation of the ratio's denominator is larger than about 0.1. Active imputation or passive imputation after log-transformation is preferable. © 2013 The Authors. Statistics in Medicine published by John Wiley & Sons, Ltd.