Development of a transformation model to derive general population-based utility: Mapping the pruritus-visual analog scale (VAS) to the EQ-5D utility

Mapping Studies to Estimate Health-State Utilities From Nonpreference-Based Outcome Measures: A Systematic Review on How Repeated Measurements are Taken Into Account

OBJECTIVES

Mapping algorithms are developed using data sets containing patient responses to a preference-based questionnaire and another health-related quality-of-life questionnaire. When data sets include repeated measurements from the same individuals over time, the assumption of observations' independence, required by standard models, is violated, and standard errors are underestimated. This review aimed to identify how studies deal with methodological challenges of repeated measurements, provide an overview of practice to date, and potential implications for future work.

METHODS

We conducted a systematic literature search of MEDLINE, Cumulative Index to Nursing and Allied Health Literature, specialized databases, and previous systematic reviews. A data template was used to extract, among others, start and target instruments if the data set(s) used for estimation and validation had repeated measurements per patient, used regression techniques, and which (if any) adjustments were made for repeated measurements.

RESULTS

We identified 278 publications developing at least 1 mapping algorithm. Of the 278 publications, 121 used a data set with repeated measurements, among which 92 used multiple time points for estimation, and 39 selected specific time points to have 1 observation per participant. A total of 36 studies did not account for repeated measurements. An adjustment was conducted using cluster-robust standard errors (21), random-effects models (30), generalized estimating equations (7), and other methods (7).

CONCLUSIONS

The inconsistent use of methods to account for interdependent observations in the literature indicates that mapping guidelines should include recommendations on how to deal with repeated measurements, and journals should update their guidelines accordingly.

Feasibility of Deriving Health State Utilities in Mycosis Fungoides Cutaneous T-Cell Lymphoma Using Mapping Algorithms

BACKGROUND

A prospective, observational, US-based study (PROVe) used three questionnaires (Pruritus-VAS, Skindex-29, MF/SS-CTCL QoL) to assess quality of life in patients diagnosed with mycosis fungoides cutaneous T-cell lymphoma (MF-CTCL); however, none of these studies was provided with a preference-based algorithm yielding health state utility values (HSUVs).

OBJECTIVE

This study aimed to assess the feasibility of deriving HSUVs from published mapping algorithms by comparing mapped utilities with the HSUVs reported in the MF-CTCL literature.

METHODS

We searched PubMed, the School of Health and Related Research Health Utility Database (ScHARRHUD), and the Health Economics Research Centre (HERC) database of mapping studies (version 7.0) to identify any studies mapping Pruritus-VAS, Skindex-29, or MF/SS-CTCL QoL to a preference-based instrument (ideally, EQ-5D), and any studies assessing HSUVs in MF-CTCL. Two algorithms from a recent study that mapped Pruritus-VAS onto EQ-5D-3L were applied to the PROVe patient-level data. We performed multiple imputation to handle missing VAS data, calculated average mapped utilities in the whole sample, and compared them with relevant factors using the t-test and one-way analysis of variance (ANOVA).

RESULTS

Overall, 298 patients provided 1441 Pruritus-VAS scores over a 2-year follow-up (1-21 visits per patient). The average mapped HSUVs ranged between 0.950 and 0.999 depending on the algorithm applied and imputation of missing data. In subgroup analysis, significant differences (p < 0.05) were observed according to age, race, and cancer stage. A few previous studies that collected HSUVs from MF-CTCL patients reported mean values of between 0.82 and 0.87 using time trade-off, 0.63 and 0.83 using EQ-5D, and 0.51 and 0.69 using the HUI3.

CONCLUSIONS

The HSUVs derived by applying published mapping algorithms to PROVe Pruritus-VAS data appeared largely overestimated if compared with the existing literature. More research is required to understand the applicability of existing mapping algorithms and to develop new mapping algorithms in MF-CTCL.

Omega-3 fatty acids for uremic pruritus: A meta-analysis of randomized controlled trials

Uremic pruritus (UP) is common in the late stages of chronic kidney disease. Currently, there is a lack of effective treatment for UP. Limited evidence exists on the therapeutic effect of omega-3 fatty acid (O3FA). The aim of this study was to evaluate the efficacy of O3FA supplements in UP patients. We evaluated the efficacy of O3FA supplements in patients with UP through a systematic review and a meta-analysis of randomized control trials retrieved from PubMed, Embase, Cochrane Library, CINAHL, and ClinicalTrials.gov databases. The included studies were summarized and assessed for the risk of bias, and pruritus assessment results were analyzed. To compared with a controlled group, five articles including 164 participants published between 2012 and 2019 using different pruritus scales reported that patients taking O3FA supplement exhibited no significant decrease in the pruritus score (standardized mean difference [SMD] =1.34, 95% confidence interval [CI] = -2.70-0.01, P = 0.05), but three articles using same pruritus scale significant decrease Duo pruritus score (SMD = -0.85, 95% CI = -1.39 to -0.30, P < 0.05). O3FA supplement could be an appealing complementary therapy for UP patients. More rigorously designed studies are needed before recommending the O3FA supplement.

Clinical Efficacy and Safety of Sodium Thiosulfate in the Treatment of Uremic Pruritus: A Meta-Analysis of Randomized Controlled Trials

Uremic pruritus is a distressful complication of chronic kidney disease and results in impaired quality of life and higher mortality rates. Intravenous sodium thiosulfate has been reported to alleviate pruritus in hemodialysis patients. We performed a systematic review and meta-analysis to estimate the efficacy of intravenous sodium thiosulfate in patients with uremic pruritus. A systematic search of electronic databases up to June 2021 was conducted for randomized controlled trials that evaluated the clinical effects of sodium thiosulfate in the management of patients with uremic pruritus. Two reviewers selected eligible articles and evaluated the risk of bias; the results of pruritus assessment and uremic pruritus-related laboratory parameters in selected studies were analyzed. There are four trials published between 2018 and 2021, which include 222 participants. The sodium thiosulfate group displayed significant decrease in the pruritus score (standardized mean difference = -3.52, 95% confidence interval = -5.63 to -1.41, p = 0.001), without a significant increase in the adverse effects (risk ratio = 2.44, 95% confidence interval = 0.37 to 15.99, p = 0.35) compared to the control group. Administration of sodium thiosulfate is found to be a safe and efficacious complementary therapy in improving uremic pruritus in patients with chronic kidney disease.

Use of Fresh Scalp Allografts From Living Relatives for Extensive Deep Burns in Children: A Clinical Study Over 7 Years

Conventionally, pediatric patients with major burns need frozen cadaveric allografts to save their lives. However, these allografts are insufficient in many burn units because of cultural and local governmental laws in China. This paper reported 22 pediatric patients with major burns who received fresh scalp allografts from their parents, siblings, or relatives from January 2011 to December 2017. These 22 pediatric patients sustained deep partial-thickness to full-thickness burns involving 40% total body surface area (TBSA) on average. Wounds were covered with fresh scalp allografts alone or with postage stamp autografts and fresh scalp allografts post excision. Data were collected from medical files of the treated patients, including sex, age, etiology of burn injury, abbreviated burn severity index (ABSI), and TBSA. Postoperative variables included early survival rate of skin grafts, mean time to rejection, length of hospital stay (LHS), healing time of donor sites, and follow-up complications of donors. The 1-year survival rate of the 22 pediatric patients included into the study was 100%. The early survival rate of the scalp allografts was similar to the autografts. The mean time to rejection was 15.5 ± 3.60 days. The average LHS was 58 days. All donor sites healed within 7.6 days on average, without scar formation, alopecia areata, or folliculitis. Following up data of the donors revealed a full psychological sense of accomplishment and no regrets of donating the scalp to save the burned children. Therefore, the use of fresh scalp allografts is a feasible alternative to save pediatric patients with major burns when frozen allografts are unavailable.

The added value of extending the EQ-5D-5L with an itching item for the assessment of health-related quality of life of burn patients: an explorative study

INTRODUCTION

Health-related quality of life (HRQL) is an important outcome in burn care and research. An advantage of a generic HRQL instrument, like the EQ-5D, is that it enables comparison of outcomes with other conditions and the general population. However, the downside is that it does not include burn specific domains, like scar issues or itching. Adding extra items to a generic instrument might overcome this issue. This study explored the potential and added value of extending the EQ-5D-5L with a burn-specific item, using a itching item as an example.

METHODS

The EQ-5D-5L and the Patient and Observer Scar Assessment Scale (POSAS) was completed by adult patients 5-7 years after injury. A separate POSAS itching item was used to study the added value of an itching item for the EQ-5D-5L. The EQ-5D-5L + Itching was created by adding the POSAS itching item to the EQ-5D-5L. Five psychometric properties were compared between EQ-5D-5L and EQ-5D-5L + Itching: distribution (e.g. ceiling), informativity cf. Shannon's indices, convergent validity, dimension dependency, and explanatory power respectively.

RESULTS

A total of 243 patients were included, of whom 49% reported any itching on the POSAS. Adding an itching item to the EQ-5D-5L decreased the ceiling effect, and resulted in increased absolute informativity (H' = 4.76 vs. H' = 3.64) and relative informativity (J' = 0.34 vs. J' = 0.31). The extra itching item decreased the convergent validity (Spearman's rank correlation coefficient = -0.51 vs. -0.59). Mutual dependency of dimensions existed, showing that all other items were dominant over the itching item. Adding the itching item to the standard EQ-5D-5L barely improved explanatory power (49.3% vs. 49.0%).

CONCLUSIONS

PThe present study showed adding a burn-specific item to the EQ-5D-5L is possible and has potential. However, 5 to 7 years after injury, adding an itching item to the EQ-5D-5L provides little additional information; the gain in terms of added value is relatively small. Apart from instances where itching information is specifically needed, a strong case is not present for adding an itching item to the EQ-5D-5L for long-term (>5 yr after burns) HRQL assessment in burn patients. In early time periods after burn, the added value might be greater and we recommend exploring this potential in future studies, ideally on multiple timepoints after burn.

An Updated Systematic Review of Studies Mapping (or Cross-Walking) Measures of Health-Related Quality of Life to Generic Preference-Based Measures to Generate Utility Values

BACKGROUND

Mapping is an increasingly common method used to predict instrument-specific preference-based health-state utility values (HSUVs) from data obtained from another health-related quality of life (HRQoL) measure. There have been several methodological developments in this area since a previous review up to 2007.

OBJECTIVE

To provide an updated review of all mapping studies that map from HRQoL measures to target generic preference-based measures (EQ-5D measures, SF-6D, HUI measures, QWB, AQoL measures, 15D/16D/17D, CHU-9D) published from January 2007 to October 2018.

DATA SOURCES

A systematic review of English language articles using a variety of approaches: searching electronic and utilities databases, citation searching, targeted journal and website searches.

STUDY SELECTION

Full papers of studies that mapped from one health measure to a target preference-based measure using formal statistical regression techniques.

DATA EXTRACTION

Undertaken by four authors using predefined data fields including measures, data used, econometric models and assessment of predictive ability.

RESULTS

There were 180 papers with 233 mapping functions in total. Mapping functions were generated to obtain EQ-5D-3L/EQ-5D-5L-EQ-5D-Y (n = 147), SF-6D (n = 45), AQoL-4D/AQoL-8D (n = 12), HUI2/HUI3 (n = 13), 15D (n = 8) CHU-9D (n = 4) and QWB-SA (n = 4) HSUVs. A large number of different regression methods were used with ordinary least squares (OLS) still being the most common approach (used ≥ 75% times within each preference-based measure). The majority of studies assessed the predictive ability of the mapping functions using mean absolute or root mean squared errors (n = 192, 82%), but this was lower when considering errors across different categories of severity (n = 92, 39%) and plots of predictions (n = 120, 52%).

CONCLUSIONS

The last 10 years has seen a substantial increase in the number of mapping studies and some evidence of advancement in methods with consideration of models beyond OLS and greater reporting of predictive ability of mapping functions.