Table 2

Risk of bias assessment

Study1. Target population approximates typical national population seeking care for LBP*2. Representative sampling frame3. Random selection/census used4. Minimal non-response bias5. Appropriate mode of data collection6. Acceptable case definition7. Appropriate study instrument8. Same mode of data collection for all9. Appropriate delay between index visit and referral*10. Appropriate numerator/denominatorSummary risk of bias
Allen et al 31 –+++++++++Moderate
Ammendolia et al 32 –++–++++++Moderate
Blackmore et al 33 +++–++++–+Moderate
Britt et al 34 +++–++++++Low
Carey et al 35 ++–+––++–+High
Charlesworth et al 36 +–+++–++–+High
Childs et al 37 +–++++++–+Moderate
Crow and Willis38 +–++++++–+High
Dey et al 7 –++++–++–+High
Feuerstein et al 39 +–+––––+–+Moderate
Friedman et al 40 ++++++++++Low
Fritz et al 41 –++++––+–+High
Fritz et al 42 +–++++++–+Moderate
Fritz et al 43 ––++++++–+Moderate
Ganduglia et al 44 ––+++–++–+High
González-Urzelai et al 45 –+++++++++Moderate
Graves et al 46 ––––+–++–+High
Graves et al 47 –+––+–++–+High
Hong et al 14 +–++++++++Low
Isaacs et al 48 +–+++–++++Moderate
Jackson and Browning49 +–++++++–+Moderate
Kerry et al 8 –––++–++++High
Kost et al 50 +–++++++–+Moderate
Kovacs et al 51 +–+–+–++++Low
Licciardone52 +++++++++–Low
Lin et al 53 ––++++++–+Moderate
Love et al 54 –++++–++–+High
May et al 55 ––+++–++++Moderate
Michaleff et al 56 +++–+–++++Low
Muntión-Alfaro et al 57 ++++++++–+Moderate
Nelson et al 58 ––+++++––+Moderate
Nunn et al 59 +–++++++++Low
Pham et al 60 –+++++++–+High
Rao et al 61 +++++–++++Low
Rizzardo et al 62 +–––++++++Moderate
Rosenberg et al 63 ++++++++–+Moderate
Salacka et al 64 –++–+–++–+High
Schlemmer et al 65 ++++++++++Low
Tacci et al 66 ––++++++++High
Tan et al 10 ––++++++++Moderate
Thackeray et al 67 ++++++++++Moderate
Walker et al 68 –––+++++–+High
Weiner and MacKenzie69 ++++++++++Low
Williams et al 9 ++++++++++Low
Wilson et al 70 –+++–––+++Moderate

  • *Modification was made to two of the original 10 items19: the definition of the target population (item 1) was modified to include only patients seeking care for LBP. We did not downgrade for geographic location or single health insurer. The length of the shortest prevalence period (item 9) was modified to the delay between index visit and referral/imaging event (low risk ≤4 weeks).