A systematic review of cellular therapies for the treatment of limbal stem cell deficiency affecting one or both eyes

PURPOSE

This systematic review (SR) assessed the efficacy, safety and cost-effectiveness of cell-based therapy to manage limbal stem cell deficiency (LSCD), a sight-threatening orphan condition most frequently associated with severe chemical or thermal burns. LSCD has historically been treated by transplanting limbal tissue. In 1997, a new treatment, cultured limbal epithelial autografts, was described for unilateral LSCD. In cases of bilateral disease cultured autologous oral mucosa stem cells have been used. The relative efficacy of different cultured tissue procedures is unknown.

METHODS

A protocol was registered with PROSPERO (CRD42017081117). Searches were conducted in 14 databases and 6 conference websites. Two reviewers independently selected studies, conducted data extraction and assessed risk of bias. One reviewer extracted individual patient data (IPD); a second checked extracted data. Data were assessed to determine the feasibility of statistical analysis, with Bayesian synthesis used to estimate improvement achieved by different treatments.

RESULTS

Fifty-two studies were eligible for inclusion (1113 eyes); 41 studies (716 eyes) reported IPD. No evidence was identified on cost-effectiveness. This SR was unable to confirm that any of the types of ex vivo cultured stem cell transplants identified for LSCD treatment were statistically superior when assessed against the outcomes of interest.

CONCLUSIONS

We believe this SR is the first to include IPD analysis of LSCD data. There is no evidence for the superiority of any method of limbal stem cell transplant. Confirmation of the safety and efficacy of this treatment modality is challenging due to heterogeneity within and between the studies identified. Therefore, recommendations for future research are proposed.

A statistical approach to designing search filters to find systematic reviews: objectivity enhances accuracy

Search filters are increasingly used to search medical databases to identify specific topics or study designs. In particular, search filters have been designed to help health-care professionals identify systematic reviews of the effectiveness of health interventions. Identifying systematic reviews in databases such as MEDLINE is problematic and research has previously been undertaken into methods to design search filters that retrieve systematic reviews effectively. The aim of this study was to improve previously developed methods to derive a more objective search strategy to identify systematic reviews in MEDLINE. A ‘quasi-gold standard’ collection of known systematic reviews was identified. A frequency analysis of words within a subset of the ‘quasi-gold standard’ was undertaken followed by a statistical analysis of the most frequently occurring words. This analysis determined which terms would best distinguish between systematic reviews, non-systematic reviews and non-reviews. The performance of the best models was tested on the remaining subset of ‘quasi-gold standard’ records and then using the OVID interface to MEDLINE. The best model had a sensitivity of 73.4% for systematic reviews in the test set and 84.2% when used with the validation set. The best model had a specificity of 98.3% in the test set and 93% in the validation set. When tested on the same ‘quasi-gold standard’ using OVID MED-LINE the model showed 100% sensitivity and 4.4% precision. The number of times a term occurs in a record adds discriminatory power to the search strategy. Apparently highly relevant terms chosen subjectively do not perform as well as those derived by a statistical approach. Some search terms may not immediately seem useful in identifying systematic reviews, but when used in combination with other terms they prove to be highly discriminating. The best performing filters were tested on the OVID interface, but without frequency and term weightings. Their performance was also compared to previously published filters. One of the strategies was found to perform better with respect to sensitivity than previously published filters, although with lower precision.

General health status measures for people with cognitive impairment: learning disability and acquired brain injury

BACKGROUND

Currently there is a wide range of health status measures that aim to assess general health status in people with cognitive impairment. However, the validity and/or applicability to this patient group are largely unknown. This has implications for the assessment of treatment outcomes and rehabilitation, for prognostic purposes, for planning services, and for determining the benefits and adverse effects of health technologies targeted at these patient groups.

OBJECTIVES

(1) To identify the general health status measures that have been validated in patients with cognitive impairment. (2) To assess the extent to which these measures have been validated. (3) To draw out the implications of the findings for the use of existing measures and for future primary research in this area. METHODS.

SELECTION CRITERIA

Studies that assessed general health status in people with cognitive impairment due to acquired brain injury (traumatic brain injury, cerebro-vascular accident or multiple sclerosis (MS)) or learning disability (LD) were included in the review. Studies that used general health status instruments measuring only one general health dimension, and studies that only featured participants with cognitive impairment due to dementia were excluded. METHODS.

SEARCH STRATEGY

A wide range of relevant databases were searched for studies on cognitive impairment, general health status measures, and validation of health status measures. A handsearch of general health status bibliographies was also conducted. Data were collected on the general health status measure used, the population characteristics, aims of the study, validity details, and conclusions.

RESULTS

The review includes data from 71 studies, reported in 83 separate publications. In total 34 different general health status measures were described in the 83 publications, with the Sickness Impact Profile (SIP) and the Short Form-36 (SF-36) the most frequently used measures (20 and 19 studies, respectively). These studies included a total of 98 instrument validations, 52 of which definitely or probably included people with cognitive impairment. Six measures were extensively validated (quality scores ranged from 0.25 to 0.5, on a scale from 0 to 1) in studies in which more than 50% of the respondents were people with cognitive impairment. A further three measures were also validated in studies in which more than 50% of the respondents were people with cognitive impairment, but their level of validation was more limited (quality scores ranged from 0.1 to 0.2). Five measures were validated in studies in which 20-50% of the respondents were cognitively impaired, which may limit their relevance to participants with cognitive impairment (quality scores ranged from 0.1 to 0.6). The SF-36 was also validated in two studies in which 20-50% of the respondents were cognitively impaired and the quality score was 0.3. Finally, nine of the measures were only validated in studies in which less than 20% of the respondents were cognitively impaired. For these measures it was unclear whether the findings applied to people with cognitive impairment.

CONCLUSIONS

Very few measures have been validated specifically for cognitively impaired respondents. Studies where at least 50% of the respondents were cognitively impaired generally showed poorer validity results compared with studies with fewer cognitively impaired persons, indicating that general health status measures designed for the general population are not automatically suitable for people with cognitive impairment. The few measures that were specifically developed for people with cognitive impairment also reported poor validity results. Therefore, there are no validated instruments available for use in cognitively impaired respondents; existing measures, specifically designed for use in these populations, should be used with caution. The most promising measure is the MS-Quality of Life Interview (MS-QLI) for MS patients. The MS-QLI was thoroughly validated in 300 MS patients and the results were good, except for the 'social function' subscale. However, only 20-50% of the respondents in this study had cognitive impairment. Most information on the validity of general health status measures was found in studies among people with LD. For these patients, six measures were found that have been validated in a populations where more than 50% of the respondents were cognitively impaired LD patients.

CONCLUSIONS

(1) Existing general health status measures should be used with caution in individuals with cognitive impairments. (2) There is no evidence to indicate the most suitable general health status measure for use in economic evaluations of cognitive impairment. (3) There is little evidence to support the validity of proxy assessments in cognitively impaired populations. (ABSTRACT TRUNCATED)