Pyruvate‐lactate exchange and glucose uptake in human prostate cancer cell models. A study in xenografts and suspensions by hyperpolarized [1‐13C]pyruvate MRS and [18F]FDG‐PET

Reprogramming of energy metabolism in the development of prostate cancer can be exploited for a better diagnosis and treatment of the disease. The goal of this study was to determine whether differences in glucose and pyruvate metabolism of human prostate cancer cells with dissimilar aggressivenesses can be detected using hyperpolarized [1‐¹³C]pyruvate MRS and [¹⁸F]FDG‐PET imaging, and to evaluate whether these measures correlate. For this purpose, we compared murine xenografts of human prostate cancer LNCaP cells with those of more aggressive PC3 cells. [1‐¹³C]pyruvate was hyperpolarized by dissolution dynamic nuclear polarization (dDNP) and [1‐¹³C]pyruvate to lactate conversion was followed by ¹³C MRS. Subsequently [¹⁸F]FDG uptake was investigated by static and dynamic PET measurements. Standard uptake values (SUVs) for [¹⁸F]FDG were significantly higher for xenografts of PC3 compared with those of LNCaP. However, we did not observe a difference in the average apparent rate constant k_pl of ¹³C label exchange from pyruvate to lactate between the tumor variants. A significant negative correlation was found between SUVs from [¹⁸F]FDG PET measurements and k_pl values for the xenografts of both tumor types. The k_pl rate constant may be influenced by various factors, and studies with a range of prostate cancer cells in suspension suggest that LDH inhibition by pyruvate may be one of these. Our results indicate that glucose and pyruvate metabolism in the prostate cancer cell models differs from that in other tumor models and that [¹⁸F]FDG‐PET can serve as a valuable complementary tool in dDNP studies of aggressive prostate cancer with [1‐¹³C]pyruvate.     

Different distribution of the genetic subtypes of the Prader�CWilli syndrome in the elderly

The Prader–Willi syndrome (PWS) is a genetic disorder caused by the absent expression of the paternal copy of maternally imprinted genes in chromosome region 15q11–13. The frequencies of different subtypes in PWS are usually given in literature as 70% deletion, 25–30% maternal uniparental disomy (mUPD) and 3–5% others (imprinting centre (IC) defects and translocations). Little is known about factors that influence the frequency of genetic subtypes in PWS. The study sample comprised 102 adults with clinically and genetically confirmed PWS, contacted through the Dutch Prader–Willi Parent Association and through physicians specialized in treating persons with intellectual disabilities. Genetic testing showed 55 persons (54%) with a paternal deletion, 44 persons (43%) with an mUPD and 3 persons (3%) with a defect of the IC. The observed distribution in our study differed from that in literature (70% deletion, 30% mUPD), which was statistically significant (z-score: P<0.05). This was mainly caused by a higher proportion of mUPD in the advanced age groups. Differences in maternal age and BMI of persons with PWS could not explain the differences in distribution across the age groups. Our study population had a much broader age range, compared with other studies, because of a predominance of elderly people (40+ years) with PWS. In other studies, these elderly persons might have been undiagnosed and/or underreported because of a lack of genetic diagnosis. The results underline both the need for correct genetic diagnosis in all persons with PWS and adjustment of the guidelines for preventive management in adulthood.     

Block design allowed for control of the Hawthorne effect in a randomized controlled trial of test ordering

BACKGROUND AND OBJECTIVE: To evaluate the value of balanced incomplete block designs in quality improvement research, and their capacity to control for the Hawthorne effect. METHODS: General practitioners teams were randomized into three arms and received an intervention on test ordering, relating to tests for two groups of clinical problems (A tests and B tests). In the two trials within the block design, we tried to control for the Hawthorne effect by comparing the complete intervention in both arms on either the A (arm I) or B tests (arm II); the arms acted as blind controls for each other. In the classical trial, the complete intervention on B tests (arm II) was compared with a control arm without any intervention on B tests (arm III). RESULTS: The trials with the block design yielded statistically significant changes in the numbers of A tests ordered (P=.013), but not in the numbers of B tests ordered (P=.29). In the classical design, the complete intervention reached a marginally significant change in the B tests (P=.068). The Hawthorne effect was the same for both arms of the block design. In the classical design, the effect could to some extent be attributed to the Hawthorne effect. CONCLUSION: Our block design allowed us to control for the Hawthorne effect. Suitable use of block designs may further our knowledge of nonspecific effects in quality improvement research.     

Nurse telephone triage in out-of-hours GP practice: determinants of independent advice and return consultation

Background

Personal continuity is a core value for family practice, but policy and performance targets emphasise other aspects of care, particularly waiting times for consultation. This study examined patient and general practitioner (GP) perceptions of the value of personal continuity and rapid access, and the relationship between them.

Methods

Qualitative analysis of semi-structured interviews with a purposive sample of 16 GPs and 32 patients in the Lothian region of Scotland, to identify whether, how, why and in which circumstances personal continuity and rapid access were valued.

Results

From the patients' perspective, what mattered was 'access to appropriate care' depending on the problem to be dealt with. For a few patients, rapid access was the only priority. For most, rapid access was balanced against greater involvement in the consultation when seeing 'their' trusted doctor, which was particularly valued for chronic, complex and emotional problems. GPs focused on the value of personal continuity in the consultation for improving the diagnosis and management of the same kinds of problem. GPs did not perceive enabling access to be a core part of their work. There was little evidence that GPs routinely discussed with patients when or how personal continuity and access should be balanced.

Conclusion

'Access to appropriate care' from the patients' perspective is not fully addressed by GPs' focus on personal continuity, nor by performance targets focused only on speed of access. GPs need to make enabling access as much a part of their core values as personal continuity, and access targets need to be based on less simplistic measures that account for the appropriateness of care as well as speed of access.     

Identifying Diagnostic Studies in MEDLINE: Reducing the Number Needed to Read

Objectives. The search filters in PubMed have become a cornerstone in information retrieval in evidence-based practice. However, the filter for diagnostic studies is not fully satisfactory, because sensitive searches have low precision. The objective of this study was to construct and validate better search strategies to identify diagnostic articles recorded on MEDLINE with special emphasis on precision.Design. A comparative, retrospective analysis was conducted. Four medical journals were hand-searched for diagnostic studies published in 1989 and 1994. Four other journals were hand-searched for 1999. The three sets of studies identified were used as gold standards. A new search strategy was constructed and tested using the 1989-subset of studies and validated in both the 1994 and 1999 subsets. We identified candidate text words for search strategies using a word frequency analysis of the abstracts. According to the frequency of identified terms, searches were run for each term independently. The sensitivity, precision, and number needed to read (1/precision) of every candidate term were calculated. Terms with the highest sensitivity × precision product were used as free text terms in combination with the MeSH term “SENSITIVITY AND SPECIFICITY” using the Boolean operator OR. In the 1994 and 1999 subsets, we performed head-to-head comparisons of the currently available PubMed filter with the one we developed.Measurements. The sensitivity, precision and the number needed to read (1/precision) were measured for different search filters.Results. The most frequently occurring three truncated terms (diagnos*; predict* and accura*) in combination with the MeSH term “SENSITIVITY AND SPECIFICITY” produced a sensitivity of 98.1 percent (95% confidence interval: 89.9–99.9%) and a number needed to read of 8.3 (95% confidence interval: 6.7–11.3%). In direct comparisons of the new filter with the currently available one in PubMed using the 1994 and 1999 subsets, the new filter achieved better precision (12.0% versus 8.2% in 1994 and 5.0% versus 4.3% in 1999. The 95% confidence intervals for the differences range from 0.05% to 7.5% (p = 0.041) and –1.0% to 2.3% (p = 0.45), respectively). The new filter achieved slightly better sensitivities than the currently available one in both subsets, namely 98.1 and 96.1% (p = 0.32) versus 95.1 and 88.8% (p = 0.125).Conclusions. The quoted performance of the currently available filter for diagnostic studies in PubMed may be overstated. It appears that even single external validation may lead to over optimistic views of a filter’s performance. Precision appears to be more unstable than sensitivity. In terms of sensitivity, our filter for diagnostic studies performed slightly better than the currently available one and it performed better with regards to precision in the 1994 subset. Additional research is required to determine whether these improvements are beneficial to searches in practice.Biomedical databases are important sources of evidence in medical practice. However, information retrieval in such databases can become very time-consuming because searches that are likely to identify all relevant information also find many irrelevant articles.In recent years researchers have adopted various approaches in the development of search strategies to selectively retrieve different types of studies (therapy, prognosis, diagnosis and etiology) and different study designs.^1,2 Search strategies targeted at diagnostic studies have also been developed.^1,3–4 The most commonly used filter for diagnostic studies is almost certainly the one now publicly available in PubMed (Clinical Queries),⁵ which based on the work of Haynes and coworkers.¹ Their search filter with emphasis on sensitivity achieved a cross-validated mean sensitivity of approximately 87% combined with a (non–cross-validated) mean precision of approximately 8%.Compared with the filter for therapeutic studies, the diagnostic filter’s precision in particular is much lower. The main reason for this difference may be the inconsistent terminology used in diagnostic studies making them difficult to index and retrieve in electronic databases.In view of this high false-positive rate, we wondered if it would be possible to develop a more precise search strategy for selecting publications on diagnostic test evaluations without losing sensitivity. Our objective was to develop, test and validate a generic search strategy for the detection of diagnostic articles recorded on MEDLINE that can be applied in any diagnostic field in Medicine.     

Quality of life in chronic illness: children, parents and paediatricians have different, but stable perceptions

AIM: Quality of life assessments can be helpful to estimate the well-being of chronically ill children. The aim of this study was to investigate the differences in perception of health-related quality of life (HRQoL) among children, parents and paediatricians at the time of diagnosis and after initial treatment in four chronic diseases. METHODS: HRQoL was assessed with the Health Utilities Index mark 3 (HUI3). The HUI3 consists of eight attributes (vision, hearing, speech, ambulation, dexterity, emotion, cognition and pain). RESULTS: Nineteen paediatricians and 60 patients (aged 10-17 years) and their parents with newly diagnosed acute lymphoblastic leukaemia, juvenile idiopathic arthritis, asthma or with cystic fibrosis admitted for pneumonia participated in the study. Health and well-being perceptions were clearly different among paediatricians, parents and patients, both at diagnosis and after initial treatment. Perception differences were more prominent in the subjective attributes, emotion and pain. The agreement for these attributes was 23% and 5%, respectively. Paediatricians assessed the patients to have less pain than the patients and parents did. The reverse was true for the attribute emotion. At follow-up, the agreement was higher for the attributes ambulation and pain. CONCLUSION: At the onset of a chronic disease and after initial treatment, paediatricians, parents and children have different perceptions of the child's quality of life, particularly as to the subjective attributes pain and emotion. In view of these differences in perception among patients, their caregivers and paediatricians, this study suggests that whenever possible, multi-respondent assessment of HRQoL should be considered.     

The development and initial validation of the narrative foreclosure scale

Objectives: As people grow older, identity development in later life becomes a more and more relevant topic. Studying processes that hinder or promote identity development in later life is of importance. Within this broader field, there has been a growing interest in narrative foreclosure. Our goal was to develop a short, reliable and easy–to-use instrument measuring narrative foreclosure and to validate this instrument in two samples.Methods: The narrative foreclosure scale (NFS) was validated in two studies with a sample of middle-aged adults (n = 319) and a sample with older adults (n = 174). Several analyses were conducted to assess the psychometric properties, the factor-structure and incremental validity of the scale.Results: Confirmatory factor analyses generally showed an acceptable fit of the two-factor (NF-Future and NF-Past) model to the data in both samples. Both factors of the NFS demonstrated adequate to good internal consistency, with alpha coefficients ranging from .79 for NF-Past in study 2 to .88 for NF-Future in study 1. Construct validity was good as shown by moderate to large correlations to related constructs. The scale adds a unique portion of explained variance to positive mental health, thereby showing the incremental validity of the NFS.Conclusion: A reliable scale is now available that allows to study the premature hindering of identity development in older populations. The use of the NFS as a process measure in studies on the effectiveness of interventions aiming at meaning making and identity development, such as life-review therapy and narrative therapy, is also recommended.