Reporting guidelines for burden of disease studies: why and how?

Background

The Disability Adjusted Life Year (DALY) is a frequently used metric to assess burden of disease (BoD). Many independent BoD studies have been performed across Europe, showing wide variations and inconsistencies in the application and reporting of DALY specific methods. The European Burden of Disease Network (burden-eu) aims to develop guidelines for reporting DALY calculation studies which may enhance transparency and comparability of BoD estimates across Europe and beyond.

Methods

A burden-eu working group of experts generated a list of potential reporting items based on existing literature, guidance for developing guidelines and consultations with BoD experts. To pilot the drafted product, we asked BoD experts and non-experts to apply it to existing BoD studies. We received feedback and we revised the guidelines accordingly.

Results

The guide for DALY calculation studies comprises about 25 items that should be reported in BoD studies. We included information about the study setting, data input sources including methods for data corrections, DALY-specific methods (e.g., YLL life table, YLD approach, disability weights etc), data analyses, and data limitations. We also included information on how users can compare their new estimates with previously available BoD estimates.

Conclusions

We introduced a reporting instrument for DALY calculations that can be used to document input data and methodological design choices in BoD studies. The application of such guidelines will enhance usability of BoD estimates for decision-makers as well as global, regional, and national health experts.

Key messages

Fostering methodological advances and technical capacity building

Countries all over the world, and especially in Europe, are increasingly using the burden of disease approach to assess the health status of populations and to identify the main drivers of ill health. Thus, there is an increasing need for equitable capacity building on the one hand (including an improved understanding of the complex methods behind global and national burden estimates), and harmonization of methods on the other hand to keep the results comparable. Furthermore, involved researchers also strive for a platform to exchange experiences and foster collaboration.

To address the current challenges in burden of disease research, our COST Action CA18218-European Burden of Disease Network will build strongly on the COST mechanisms, such as short-term scientific missions and training schools to foster and increase capacity building activities across Europe. Our Action will also serve as a technical platform where knowledge and expertise can be shared among experienced and less experienced researchers. Collaboratively, the technical platform will provide unique opportunities for developing a joint research agenda in the domain of burden of disease, for fostering methodological developments, and for developing new collaborative research.

With this presentation, we aim to show how the COST Action is fostering methodological advances and technical capacity building, focusing on 1) the role and aim of short-term scientific missions including real case examples; 2) the concept and structure of the Action's training schools; and 3) examples of specific methodological activities underway as part of the Action. The session will conclude with an interaction with the audience during which the needs and expectations of the attendees will be elicited.

Developing a strategic plan for sustainable health inequality monitoring – the basic step towards tackling health inequalities in long run

Slovenia has had periodic reporting on health inequalities for almost a decade. The importance of reporting is well recognised and stated in the National strategy on health care 2015-2025. Yet, the assessment of the status of the national health inequality monitoring system (HIMS) conducted within the Joint Action Health Equity Europe project, made the unsystematic nature of current practices obvious. A need for developing a more systematic and sustainable HIMS and to have a long-term monitoring strategic plan in place was acknowledged.

The set-up of systematic and sustainable long-term monitoring of health inequalities will provide reliable and comparable longitudinal data on the direction, magnitude and trend of health inequalities in Slovenia. This is in turn necessary to inform any future policies and/or programmes, thus stimulating action. Furthermore, identifying relevant stakeholders will facilitate formation of a network of partners who take part in tackling health inequalities, thus allowing for a more proactive (i.e. bridging) role in addressing health inequalities in Slovenia.

The aim of this presentation is to demonstrate the process and the steps taken to prepare a document (strategic plan) detailing a systematic approach to long-term monitoring of health inequalities complete with goals, objectives, methodology, a pragmatic set of indicators and an evaluation plan that will inform and facilitate most reporting/monitoring activities

Internal initiation drives the synthesis of Ure2 protein lacking the prion domain and affects [URE3] propagation in yeast cells

The [URE3] phenotype in Saccharomyces cerevisiae is caused by the inactive, altered (prion) form of the Ure2 protein (Ure2p), a regulator of nitrogen catabolism. Ure2p has two functional domains: an N-terminal domain necessary and sufficient for prion propagation and a C-terminal domain responsible for nitrogen regulation. We show here that the mRNA encoding Ure2p possesses an IRES (internal ribosome entry site). Internal initiation leads to the synthesis of an N-terminally truncated active form of the protein (amino acids 94-354) lacking the prion-forming domain. Expression of the truncated Ure2p form (94-354) mediated by the IRES element cures yeast cells of the [URE3] phenotype. We assume that the balance between the full-length and truncated (94-354) Ure2p forms plays an important role in yeast cell physiology and differentiation.

Mandibular and temporomandibular joint arthropathy in the differential diagnosis of the parotid mass

OBJECTIVE

To increase awareness of temporomandibular joint and mandibular disease in the overall evaluation and diagnosis of the parotid mass.

STUDY DESIGN

We describe clinical presentations of pigmented villonodular synovitis and synovial chondrocalcinosis of the temporomandibular joint, as well as osteoma of the mandible, as they may initially suggest primary neoplasms of the parotid gland.

CONCLUSIONS

Preauricular swelling is a common presenting symptom for patients visiting an otolaryngologist. Often this symptom is suggestive of a parotid mass. However, lesions of the temporomandibular joint and mandible may also present in this fashion.

Conformational toxicity and sporadic conformational diseases

Spontaneous, so-called 'conformational' diseases, specially of the neurodegenerative type like Alzheimer's, are linked to certain protein types which have the normal amino-acid sequence but are misfolded and accumulate due to resistance to proteolysis. In the case of prion diseases, the 'protein only' hypothesis assumes that the misconformation of a native protein could be initiated upon interaction with a sister-protein already in the misfolded state. There is an alternative to this sister protein contamination scheme, which assumes that the misconformation is acquired upon protein synthesis, that is de novo. Misfoldling and resistance to proteolysis could result from defects responsible for shortage or inactivity of the cellular factors in charge of protein folding and degradation. The defects could have a genetic origin (the gene of the faulty factor involved could have been mutated, or control and regulation of its expression could have been altered, etc.). Alternatively, the cell's actual biosynthetic and/or proteolytic resources could have become overloaded and unavailable, due to unscheduled mass-production of proteins resulting from unscheduled cell growth or proliferation, cell stress, etc. Xenobiotics, active for instance as endocrine proliferators, stressors, or inducing copious, unscheduled gene expression, etc. could give rise to shortage of cellular factors necessary for the production of native proteins and for proteolysis. Alternatively, xenobiotics could alter expression or activity of some of these factors. In both cases, the xenobiotic could be a 'conformational toxicant' by inducing misfolding of selected proteins. The xenobiotic could trigger some conformational disease if it targets a specific protein and tissue.

Ribosome traffic in E. coli and regulation of gene expression

The ribosome traffic during translation of E. coli coding sequences was simulated, assuming that the rate of translation of individual codons is limited by the cognate tRNA availability. Actual translation rates were taken from Solomovici et al. (J. theor. Biol. 185, 511-521, 1997). The mean translation rates of the 4271 sequences cover a broad, two-fold range, whereas the local rate of translation along messengers varies three-fold on average. The simulation allows one to sketch the ribosome traffic on the polysome, in particular by providing the extent of mRNA sequences uncovered between consecutive ribosomes and the time during which these sequences are exposed. These parameters may participate in the control of mRNA stability and transcriptional polarity. By averaging the translation rates in a 17-codon window, assumed to be the sequence covered by a translating ribosome, and sliding this window along a given coding sequence, the addresses KMAX and KMIN, and the times TMAX and TMIN of respectively the slowest and the fastest translated window were determined. It is shown that under the assumptions made, TMAX sets the number of proteins translated from a given mRNA molecule per unit time, in case the delay between consecutive translation starts is below TMAX. Both windows display two strong biases, one as expected on the usage of codon frequencies, and the other surprisingly on the occurrence of amino acids.

Synonymous codon substitutions affect ribosome traffic and protein folding during in vitro translation

To investigate the possible influence of the local rates of translation on protein folding, 16 consecutive rare (in Escherichia coli) codons in the chloramphenicol acetyltransferase (CAT) gene have been replaced by frequent ones. Site-directed silent mutagenesis reduced the pauses in translation of CAT in E. coli S30 extract cell-free system and led to the acceleration of the overall rate of CAT protein synthesis. At the same time, the silently mutated protein (with unaltered protein sequence) synthesized in the E. coli S30 extract system was shown to possess 20% lower specific activity. The data suggest that kinetics of protein translation can affect the in vivo protein-folding pathway, leading to increased levels of protein misfolding.

Detection of transmembrane helical segments at the nucleotide level in eukaryotic membrane protein genes

The analysis of base distributions at the three codon positions, in sequences coding for polytopic membrane proteins from Eukaryotes, reveals a global excess of thymine and a depletion of adenine, at the second codon position. These genes were scanned using a sliding window, in which the average ratio of T over A at the second position of codons was computed. The scan shows that sharp peaks of this ratio, which are responsible for the high mean value of this parameter in the genes, correlate closely with the transmembrane segments of the membrane proteins. These results are quite similar to our previous findings for bacterial polytopic inner membrane proteins. This establishes the ratio of T over A at codon position two as a universal parameter for both the characterization of the genes of polytopic membrane proteins, and for the location of alpha-helical, transmembrane segments of these proteins.

Differential resistance to proteinase K digestion of the yeast prion-like (Ure2p) protein synthesized in vitro in wheat germ extract and rabbit reticulocyte lysate cell-free translation systems

The Ure2p yeast prion-like protein was translated in vitro in the presence of labeled [35S]methionine in either rabbit reticulocyte lysate (RRL) or wheat germ extract (WGE) cell-free systems. When subjected to proteinase K digestion, the Ure2p protein synthesized in WGE was proteolysed much more slowly compared to that synthesized in RRL; this displays fragments of about 31-34 kDa, persisting over 8 min. Thus, the digestion rate and pattern of the protein synthesized in WGE, unlike that synthesized in RRL, revealed characteristic features of the [URE3] prion-like isoform of the Ure2p protein [Masison, D.C. and Wickner, R.B. (1995) Science 270, 93-95]. Chloramphenicol acetyltransferase, synthesized under the same conditions, differed fundamentally in its proteolytic sensitivity toward proteinase K (PK); in the RRL system it was more slowly digested than in WGE, proving specific PK inhibitors to be absent in both systems. Posttranslational addition of the WGE to the RRL-synthesized Ure2p does not protect Ure2p from efficient PK degradation either. The differences in Ure2p degradation may be ascribed to a specific structure or specific states of association of Ure2p synthesized in WGE; obviously, they yield a protein that mimics the behavior of the Ure2p in [URE3] yeast strains. The present data suggest that particular conditions of the Ure2p protein translation and/or certain cellular components (accessory proteins and extrinsic factors), as well as the nature of the translation process itself, could affect the intracellular folding pathway of Ure2p leading to the de novo formation of the prion [URE3] isoform.

Does Escherichia coli optimize the economics of the translation process?

The codon translation rate is usually assumed to be proportional to the cellular concentration of the cognate tRNA, but synonymous codons sharing the same cognate tRNA may be translated at rather different rates. To account for the latter observation, we assume that the translation process is optimized in two respects: (i), the codon demand is optimized with respect to the supply of cognate tRNAs (composition of the tRNA pool); and (ii), for synonymous codons sharing the same cognate tRNA, the usage frequency of each codon correlates optimally with the stability of the codon-anticodon complex. These assumptions allow us to compute the relative rate constants of synonymous codons. Highly expressed genes, which produce 80-90% of the protein mass in the E. coli cell, appear to have selected codons which make an optimal use of the tRNA pool. Assuming the optimization criteria were valid, a list of codon translation times (in ms) were derived from available experimental data.

A method to detect transmembrane helical segments at the nucleotide level

The analysis of base distributions at the three codon positions, in sequences coding for integral inner membrane proteins from Bacteria, reveal a global excess of thymine and a depletion of adenine, at codon position two. These genes were scanned using a sliding window, in which the average ratio of T to A at the second position of codons, TA(2) (converted to a logarithm, the LTA2 ratio) was computed. The profiles obtained reveal sharp and local peaks of the LTA2 ratio, which account for the high mean values of this parameter. For inner membrane proteins of known structure, the position and extent of these peaks correlate with the location of transmembrane alpha-helices. The prediction accuracy of the detection of such structures using the LTA2 ratio compares to that obtained using algorithms based on an hydrophobicity index of amino-acids. This new criterion presents several advantages, as it deals directly with the nucleotide sequence, does not rely on the values of empirical parameters and finds direct applications in molecular biology studies. Since the nucleotide sequences of transmembrane beta-strands do not give rise to peaks in the LTA2 ratio profile, the criterion appears to characterize exclusively alpha-helical segments in transmembrane proteins.