Data screening information was taken into account in the stepwise procedure of the item reduction analysis.
This procedure resulted in 13 I, 26 A and 20 P candidate items (for details of this procedure and format of items see Additional file 1: initial item pool reduction).
After repeating the procedure of searching for items that were not invariant several times, equality constraints were lifted for two items ("failure" and "good") on the Depressive Affect and Positive Affect factor.
In a TDC-procedure, the detection of items with sufficiently pronounced scores is always concomitant with the attribution of a reference score value which is used to determine a Contrast-value.
The procedure of a one-item measurement of RTW-expectations has previously been demonstrated to be sufficient, 37 and the single item used to measure RTW-expectations in the present study has been found to measure important aspects of RTW-expectations in patients with low back pain.
ICF linking is an established procedure requiring the content of items in assessment instruments to be connected to the most precise ICF category possible: training was provided for this procedure and 10%% of full-text were double checked with regard to linking results.
This procedure identifies potential clusters of items, with a non-significant (P>0.05) difference between any two items belonging to a given cluster and, conversely, a significant (P≤0.05) difference between any two items belonging to two distinct clusters.
The protocols should include assessment of the evidence for procedures like fumigation, reuse of items, maintaining cleanliness of the environment (especially in labour rooms) and rational use of antibiotics, adapted to resource constrained settings.
The questionnaire scoring procedure requires recoding of item 3, and standardizing raw scores for calculating the arithmetic mean value ranging from 0 (lowest impact) to 10 (maximum impact).
The procedure of separately added reference items allowed, like in clinical care, monitoring of late pronounced signs and symptoms and provided data on success rate and efficacy of treatment which were not biased by the clinician or by inter-patient differences in treatment duration or number of visits.
