Elsevier

Journal of Clinical Densitometry

Volume 12, Issue 3, July–September 2009, Pages 267-271
Journal of Clinical Densitometry

Commentary
The Official Positions of the International Society for Clinical Densitometry: Perceptions and Commentary

https://doi.org/10.1016/j.jocd.2009.03.098Get rights and content

Abstract

The International Society for Clinical Densitometry (ISCD) periodically issues Official Positions (OPs) on the assessment of skeletal health in adults and children. OPs are recommendations regarding topics that include nomenclature, indications, acquisition, analysis, quality control, interpretation, reporting, and clinical utility of measuring bone density using different technologies. The purpose of these directives is to assist health care professionals in the practice of clinical densitometry. The OPs are established through a rigorous process of scientific literature review by ISCD task forces, each assigned to address a group of clinically relevant questions. The findings and recommendations of each task force are assessed and revised, as needed, by an international panel of experts. Recommendations that are felt to be appropriate for inclusion as ISCD OPs are sent to the ISCD Board of Directors for final approval. Despite having a major impact in the clinical application of bone densitometry, the ISCD OPs have not been universally adopted, in part because of misunderstanding of the process used to establish them and the way that they are intended for use in clinical practice. This is a review of the benefits and limitations of the ISCD OPs with emphasis on areas of controversy.

Introduction

The International Society for Clinical Densitometry (ISCD) is a non-profit professional society dedicated to enhancing knowledge and improving quality in the assessment of skeletal health. The ISCD strives to accomplish its mission through means that include educational venues, certification of clinicians and technologists, the Journal of Clinical Densitometry, the ISCD Annual Meeting, and recommendations, through Official Positions (OPs), for the clinical use of bone densitometry. New and revised OPs have been developed every 2 yr since 2001 at Position Development Conferences (PDCs) and are published in the Journal of Clinical Densitometry, most recently in 2008 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11.

The methodology for the conduct of the PDCs and the development of the OPs have been described in detail 6, 11. Topics for consideration are selected by the ISCD Scientific Advisory Committee and the Board of Directors based on clinical relevancy and a perceived need for standardization. Clinical questions for each topic area are assigned to specific, distinct ISCD task forces for a review of the scientific literature and evaluation using a modification of the Cochrane method (12). The literature searches are conducted using electronic databases that include PubMed, EMBASE, and MEDLINE. Appropriate publications are selected from the literature searches for further review. A report of the review and recommendations for OPs are presented by task force chairs to an international panel of experts at the PDCs. The expert panelists review the recommendations and supporting documents, make revisions when appropriate, and then propose OPs to the ISCD Board of Directors. For the 2007 PDCs, a modification of the Delphi process developed by the Research and Development (RAND) Corporation and University of California at Los Angeles (UCLA), called the RAND/UCLA appropriateness method (RAM) (13), was used. Unlike the original Delphi process, RAM provides the expert panelists with an opportunity to discuss their judgments between (in this case) 2 separate rating rounds. The potential bias of face-to-face group interactions is controlled by expert moderators who are selected according to their great breadth of knowledge in the topics under consideration, as well as leadership skills (14). RAM is a mechanism for determining whether medical procedures or indications are expected to provide a specific health benefit, designated as “appropriate,” that exceeds the potential negative consequences by such a wide margin that the procedure or indication is worth performing. Procedural or other costs are not included in this analysis. The rationale for use of RAM is based on its ability to combine the best available scientific evidence with the collective judgment of internationally recognized experts in skeletal health assessment to yield “appropriate” recommendations. Before the PDC, the clinical questions and subquestions for each topic are converted into recommendation statements by the task forces and sent to the expert panel for an initial “appropriateness” rating. The PDC requires a median value for the “appropriateness” rating to be in either the upper third or lower third of the rating continuum. Continuum is 1–9 with clusters 7–9 representing the upper third (appropriate) and clusters 1–3 representing the lower third (not appropriate) without “disagreement.” Disagreement is defined as lack of consensus, predetermined by 4 or more expert panelists having ratings in the extreme clusters 1–3 or 7–9, whereas the other expert panelists have their values in the other extreme cluster. In circumstances where the median “appropriateness” rating is less than 7, no OP is offered or further developed. In making its decisions, the expert panel considers the level of the medical evidence, expert opinion, and the clinical need for a recommendation. In some instances, regulatory issues receive consideration. The statements rated as “appropriate” with a median score of 7 or higher without “disagreement” by the expert panel are designated as potential OPs. The statements rated as “uncertain” with a median score between 4 and 6 or any median score with “disagreement” are further discussed at the PDC meeting. After the initial rating, the documents supporting the recommendations of the task forces are sent to the expert panelists for review. Task force chairs present reports on their topics supporting the “uncertain” statements to the expert panelists in closed session on the first day of the conference. These statements are then edited by task force chairs, if necessary, reflecting suggestions made by the expert panelists. Re-rating of “uncertain” statements occur during each task force chair's presentation when the PDC moderators feel there is significant likelihood of change in the opinions of the expert panel. After all statements rated as “appropriate without disagreement” are selected and all supporting evidence presented, the expert panelists perform a final rating for necessity, quality of the evidence, strength of the recommendation, and application of the recommendation. The following day, the proposed OPs with supporting evidence are presented by the task force chairs to a meeting open to the public. The public meeting is typically attended by ISCD members, industry representatives, and individuals with interest in skeletal health assessment. All participants are encouraged to provide comments and suggestions to the expert panelists. On the 3rd day, the expert panelists, in closed session, determine final wording of the proposed OPs, which are then sent to the ISCD Board of Directors for approval.

The development of the most recent OPs in 2007 was a complex, but highly-defined process that involved approx 100 participants each for the adult and pediatric PDCs. Participants, some of whom were involved in the prelude and follow-up to the PDCs for more than 24 mo, were from 19 different countries. Not surprisingly, some of the issues that were addressed at the PDC were controversial, usually because of lack of high-quality evidence, or sometimes, conflicting evidence. The selection of controversial topics was intentional, because it is often in areas of controversy that inconsistent practice patterns are seen. With bone densitometry, as with many other technical disciplines, it is generally preferable to be consistent rather than haphazard in behavior, allowing for better communication with other clinicians, investigators, and patients, and focusing attention on areas in need of further study. Clinicians must make decisions for patient care based on current best available evidence and often cannot wait until more compelling evidence may become available. The nature of the topics considered at the PDCs assures that there will be vigorous (and healthy) disagreement among experts. It is safe to state that there are no expert panelists and no ISCD Board members who agree with all ISCD OPs. It is understood by all participants in the PDCs that when better evidence becomes available, the OPs will be reconsidered for possible revision. Still, the OPs have provided clinicians, scientists, and technologists with a reference standard for quality control, data acquisition, analysis, interpretation, and reporting of bone density tests. They have advanced the field of bone densitometry by improving the quality and consistency of bone density testing, and by identifying topics requiring further study. They have refined the original World Health Organization (WHO) classification of bone mineral density as normal, osteopenia, or osteoporosis (15) so that it may be used in a consistent fashion in clinical practice. The most recent ISCD OPs have been endorsed by professional organizations that include the American Association of Clinical Endocrinologists, the American Society for Bone and Mineral Research (ASBMR), The Endocrine Society, the North American Menopause Society, and National Osteoporosis Foundation (NOF) (16).

To fully understand the role of the OPs in clinical practice and their contribution to the evaluation of skeletal health, it is instructive to view them critically and respond objectively. An essential element of all ISCD PDCs is to re-examine the procedural formats of previous PDCs and the relevance of established OPs over the course of time. By performing such a critical self-analysis before and after each PDC, the ISCD seeks to validate the clinical utility of the OPs in skeletal health assessment worldwide. The 2007 PDC was conducted as previously stated, using the universally accepted procedural format called RAM. In retrospective analysis, the RAM was found to provide benefits that are uniquely adaptable to the ISCD PDCs compared with previous formats. To evaluate the relevance of the OPs over time, it is helpful to view them critically from the perspective they do not achieve their intended purpose and thereafter responding in an objective fashion by defending their clinical utility. This is done in the following exercise, in the form of questions and answers that serve to highlight the benefits and the limitations of the OPs in proper context.

QUESTION (Q): Are the OPs evidence-based or a consensus statement?

ANSWER (A): There is perhaps no better definition of evidence-based medicine (EBM) than that of Professor David L. Sackett, of the NHS RAND Center for EBM, Oxford, UK, who described it as “the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of EBM means integrating individual clinical expertise with the best available external clinical evidence from systematic research (17). He went on to state that “EBM is not restricted to randomized trials and meta-analyses. It involves tracking down the best external evidence with which to answer our clinical questions (17).” This is exactly what occurs in the PDC process. First, questions in topic areas of clinical relevance are formulated. Then, a review of the current best evidence is undertaken. Finally, after consideration of the evidence, the clinical expertise of the expert panelists is applied to developing the OPs. The RAM is a well-established methodology (13) that was used for the 2007 PDC because it allows for evaluation of the current best medical evidence with the collective judgment of worldwide experts to develop recommendations that are patient- and technology-specific. Consensus plays no role in establishing the OPs and thus, the PDC cannot be labeled as a consensus conference. Every OP from the 2007 PDC was rated according to the following categories:Appropriateness

  1. Statements that the expert panel rated as “appropriate without disagreement” according to predefined criteria derived from the RAM were referred to the ISCD Board of Directors with a recommendation to become ISCD OPs. A statement was defined as “appropriate” when the expected health benefit exceeded the expected negative consequences by a significant margin such that it was worth performing.

Necessity
  1. Recommended OPs that were rated by the expert panel were then rated according to necessity to perform in all circumstances, that is, whether the health benefits outweighed the risks to such an extent that it must be offered to all patients. Necessity rating was conducted in a similar fashion as the appropriateness rating, in that each OP had to be rated as necessary without disagreement using similar predefined RAM criteria.

Quality of the evidence
  1. Good: Evidence includes consistent results from well-designed, well-conducted studies in representative populations.

  2. Fair: Evidence is sufficient to determine effects on outcomes, but the strength of the evidence is limited by the number, quality, or consistency of the individual studies.

  3. Poor: Evidence is insufficient to assess the effects on outcomes because of limited number or power of studies, important flaws in their design or conduct, gaps in the chain of evidence, or lack of information.

Strength of recommendations
  1. A: Strong recommendation supported by the evidence

  2. B: Recommendation supported by the evidence

  3. C: Recommendation supported primarily by expert opinion

Application of recommendations
  1. W: Worldwide recommendation

  2. L: Application of recommendation may vary according to local requirements

Although it would be ideal for all clinical decisions with individual patients to be made on the basis of the highest levels of medical evidence (e.g., high-quality randomized controlled clinical trials and meta-analyses of the same direction of effect), clinicians must make many decisions every day for individual patients based on insufficient evidence. The OPs are intended to provide a guide to clinicians for clinical decisions that must be made in the setting of a wide range of levels of evidence.

Q: Are the OPs applicable worldwide?

A: In the selection of task force and expert panel members, the ISCD has made a major effort to have broad international representation. For the 2007 Pediatric PDC, 2 of 5 task force chairs and co-chairs were non–USA-based, as were 3 of 4 task force advisors, and 8 of 14 expert panel members. For the 2007 adult PDC, 3 of 6 task force chairs and co-chairs were non–USA-based, as were 4 of 8 task force advisors and 4 of 12 expert panel members. Societies with large components of non-USA members (e.g., ASBMR, International Bone and Mineral Society, International Osteoporosis Foundation), as well as the NOF, were invited to select a representative to participate on the expert panels. Of the 22 current ISCD Board members, 8 are non–USA-based. Recognizing that there may be regional differences in the applicability of OPs, each was rated according to whether it applied worldwide or varied according to local requirements. No OP was rated for applicability to an individual country. Finally, it should be noted that the major focus of the 2007 Adult PDC was the use of non-central dual-energy X-ray absorptiometry (DXA) technologies for the assessment of skeletal health—a topic that is of greatest interest outside USA.

Q: Are the OPs in conflict with the WHO with regard to reference databases, skeletal site selection for diagnostic classification, terminology (“low bone mass” instead of “osteopenia”) and the use of the fracture risk assessment tool (FRAX)?

A: The most recent ISCD OPs were established in mid-2007, before the release of the WHO technical report on the assessment of osteoporosis at the primary care level (18) and FRAX (19) in early 2008. However, the ISCD has been cognizant and supportive of, and participated in, WHO activities in these areas. The WHO preference on reference databases was discussed at length at the 2005 PDC, when it was agreed to adopt the OP that “The WHO international reference standard for osteoporosis diagnosis is a T-score of −2.5 or less at the femoral neck,” and “The reference standard from which the T-score is calculated is the female, white, aged 20–29, National Health and Nutrition Examination Survey III (NHANES III) database” (20), with worldwide applicability. At the same time, it was recognized that for individual patients in clinical practice, “Osteoporosis may be diagnosed in postmenopausal women and in men aged 50 and older if the T-score of the lumbar spine, total hip, or femoral neck is −2.5 or less” and “in certain circumstances, the 33% radius (also called 1/3 radius) may be used” (20), with applicability that may vary according to local requirements. The wording of these OPs was carefully crafted to meet the needs of the WHO in establishing an international reference standard, whereas at the same time allowing clinicians to manage individual patients according to local requirements. Historically, these skeletal sites were selected to help clinicians make practical diagnostic decisions in individual patients, because the original 1994 WHO technical report (15) did not identify which skeletal sites could be used for diagnosis. With the passage of time, it is likely that there will be greater standardization in the use of reference databases and diagnostic criteria for osteoporosis, as well as greater emphasis on fracture risk assessment. The ISCD supports the use of the NHANES III reference database at the hip for T-score calculation, using a female reference database for women and a male reference database for men, whereas the WHO supports using the NHANES III reference for both men and women. Reasonable evidence-based arguments can be made for both positions. As more evidence becomes available, it will undoubtedly be reconsidered at future PDCs, a standard policy of the ISCD.

The ISCD OP uses the word “osteopenia” for diagnostic classification, but states that while the term “osteopenia” is retained, “low bone mass” or “low bone density” is preferred (6). The rationale for this OP has been published (21), recognizing that the quality of the evidence is poor and the strength of the recommendation is weak. This is certainly a very minor issue, but “osteopenia” was felt to have greater utility in the setting of epidemiologic research than in the care of individual patients, where to some it could imply a disease state with high fracture risk, which may not be the case.

The ISCD provided financial support for the development of FRAX and sent 3 representatives to participate in the meeting of the WHO Scientific Group on the assessment of osteoporosis at primary care level, held in Brussels, Belgium on May 5–7, 2004 (22). The ISCD participated in reviewing and suggesting revisions to the WHO technical report on fracture risk assessment (18). The OPs state that “The ISCD favors the use of absolute fracture risk prediction when such methodologies are established (6), and continues to do so now that they are established. Just as there are shortcomings, deficiencies, and disagreements with some of the ISCD OPs, so are there with the use of FRAX. For example, FRAX estimates fracture risk based on “dichotomized” risk factors (e.g., a yes or no input for clinical risk factors that are associated with a range of fracture risk depending on dose or duration of exposure), thereby overestimating or underestimating the actual fracture risk in some individual patients. This does not mean that the OPs and FRAX should not be used, but that experts work together to continually improve them.

Q: Why does the ISCD recommend the use of Z-scores for premenopausal women and men under age 50?

A: The rationale for the OP stating that “Z-scores, not T-scores, are preferred” (6) in these populations is based on clinical pragmatism. It was felt by the expert panelists that the use of T-score in premenopausal women and men under age 50 might lead to inappropriate application of the WHO diagnostic criteria, overestimation of fracture risk, and unnecessary treatment with pharmacologic agents. It was also recognized that in many of these patients the T- and Z-scores are likely to be very similar or identical, and that in the hands of an informed health care provider, excellent medical care can be given using one or the other.

Q: Why is the use of vertebral fracture assessment (VFA) by DXA encouraged, when it is not widely available outside USA.

A: There is strong evidence that a prevalent vertebral fracture, whether it is clinically evident or detected standard X-ray or VFA, is predictive of future fracture (5). FRAX allows for clinical or radiographic vertebral fracture input, thereby accounting for the influence of prevalent vertebral fracture on fracture risk assessment and allowing for it to affect treatment decisions. Where VFA is available, it is a useful way of diagnosing vertebral fractures with greater patient convenience, less cost, and lower radiation exposure than conventional X-ray. Where DXA is not available, then VFA cannot be used.

In conclusion, the ISCD OPs are recommendations and not guidelines for the use of clinical tools for the assessment of skeletal health in individual patients. They are periodic snapshots of current best medical evidence as evaluated by the clinical judgment of an international panel of experts using a methodology for analysis and construction that is accepted worldwide. The clinical questions that are addressed are often selected because practicing physicians and technologists must make decisions that impact the care of patients, even when the medical evidence is limited or absent. Some OPs are arbitrary (e.g., nomenclature: DXA, not DEXA), but are established because there is value in standardizing methods of communication. Some are controversial (e.g., the use of a male reference database rather than a female database for interpretation of bone density in men), but represent a dedicated effort on behalf of many of the experts in the field to interpret evidence that is inconsistent or conflicting. All OPs are subject to periodic review and revision, when appropriate, at subsequent PDCs. Recommendations for further study accompany the release of OPs, in the hope that better evidence at the time of future PDCs can be considered for revising PDCs that are no longer current. When there is a lag-time between important new evidence and revision of an outdated OP, and when there is disagreement about an OP by knowledgeable clinicians and scientists, it is then particularly important that good clinical judgment be used in making patient care decisions.

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