Screening for Postmenopausal Osteoporosis: Summary of the Evidence, Appendix Table 1. Summary of Evidence Quality

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Appendix Table 1. Summary of Evidence Quality

Linkage (Figure 1)	Key Questions	Evidence Code¹	Internal Validity	External Validity
Arrow 1:	Does screening using risk factor assessment or bone density testing reduce fractures?	None
Arrow 2:	Does risk factor assessment accurately identify identify women who may benefit from bone density testing?	II-2	Poor-good: small studies, risk assessment instruments often not validated.	Poor-fair: no instruments used widely for screening purposes although some were developed from community-based studies.
Arrow 3:	Do bone density measurements accurately identify women who may benefit from treatment?	II-2	Fair-good: studies indicate the short-term predictability for fracture.	Fair: not known how well results of studies translate to practice.
Arrow 4:	What are the harms of screening?	II-2, III	Poor-fair: small studies, descriptive.	Poor: small studies, selected participants.
Arrow 5:	Does treatment reduce the risk of fractures in women identified by screening?	I	Good: bisphosphonate trials indicate fracture prevention.	Poor-fair: participants of trials may be different than primary care patients.
Arrow 6:	What are the harms of treatment?	I, II-2	Poor-good: long-term effects of newer agents not known.	Poor-fair: difficult to know how risks impact individual patients.

¹Evidence codes based on study design categories (22):
I = randomized, controlled trials.
II-1 = controlled trials without randomization.
II-2 = cohort or case-control analytic studies.
II-3 = multiple time series, dramatic uncontrolled experiments.
III = opinions of respected authorities, descriptive studies.
²Based on criteria developed by the U.S. Preventive Services Task Force (22).

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