How are the numbers calculated in a Summary of Findings Table? There - - PDF document

How are the numbers calculated in a Summary of Findings Table? There are 3 main numbers calculated and presented for an outcome in a Summary of Findings Table:

• 1. The relative effect (e.g. Relative Risk, Odds Ratio, Mean Difference or Standardised Mean Difference)
• 2. The assumed risk or score in a group of people who do not receive the intervention (e.g. baseline risk)
• 3. The corresponding risk or score in a group of people who do receive the intervention.

Outcomes Illustrative comparative risks* (95% CI) Relative effect (95% CI) No of Participants (studies) Quality of the evidence (GRADE) Comments Assumed risk usual care Corresponding risk self management Death (follow‐up: 12 months) Medium risk population RR 0.93 (0.85 to 1.02) 2530 (8)



moderate 649 per 1000 604 per 1000 (552 to 662) Quality of Life St George's Respiratory Questionnaire. Scale from: 0 to 100. (follow‐up: 3‐12 months) The mean quality of life ranged across control groups from 38 to 60 points The mean quality of Life in the intervention groups was 2.58 lower (5.14 to 0.02 lower) 698 (7)



moderate Lower score indicates better quality of life. A change of less than 4 points is not shown to be important to patients.

These numbers are based on the meta‐analysis of an outcome and the absolute effects across different groups of people at different risks. Some numbers are automatically imported and calculated in GRADEpro, but other numbers need to be entered into GRADEpro manually and require some decision making on the part of the author. As can be seen in the outcomes in the Summary of Findings Table above, the numbers are calculated and presented differently depending on the type of outcome: dichotomous or continuous. Presentation of a DICHOTOMOUS OUTCOME (Relative Risk and Odds Ratio) Example: Risk of death with the use of low‐molecular weight heparin (LMWH) versus placebo (control)

Outcomes Illustrative comparative risks* (95% CI) Relative effect (95% CI) No of Participants (studies) Quality of the evidence (GRADE) Comments Assumed risk usual care Corresponding risk self management Death (follow‐up: 12 months) Medium risk population RR 0.93 (0.85 to 1.02) 2530 (8)



moderate 649 per 1000 604 per 1000 (552 to 662)

The relative risk with confidence intervals and the number of participants and number of studies are automatically taken from the meta‐analysis and added to the SoF.

Study or Subgroup Lebeau 1994 Altinbas 2004 Agnelli 2009 Weber 2008 Klerk 2005 Sideras 2006 Perry 2010 Kakkar 2004 Total (95% CI) Total events Heterogeneity: Tau² = 0.01; Chi² = 10.75, df = 7 (P = 0.15); I² = 35% Test for overall effect: Z = 1.57 (P = 0.12) Events 96 22 333 8 88 40 45 103 735 Total 138 42 769 10 148 68 99 190 1464 Events 110 30 155 10 107 41 32 109 594 Total 139 42 381 10 154 69 87 184 1066 Weight 20.6% 6.1% 19.7% 6.1% 16.9% 8.6% 6.0% 16.0% 100.0% M-H, Random, 95% CI 0.88 [0.76, 1.01] 0.73 [0.52, 1.04] 1.06 [0.92, 1.23] 0.81 [0.57, 1.14] 0.86 [0.72, 1.01] 0.99 [0.75, 1.31] 1.24 [0.87, 1.75] 0.92 [0.77, 1.09] 0.93 [0.85, 1.02] Heparin Control Risk Ratio Risk Ratio M-H, Random, 95% CI 0.5 0.7 1 1.5 2 Favours heparin Favours control

Authors must determine what assumed risk to enter and then the corresponding risk is automatically calculated. Determine the assumed risk Authors can choose which assumed risk to present. There are 4 suggestions for what to choose:

• 1. present mean baseline risk from the studies in the meta‐analysis. GRADEpro automatically calculates the mean as

the total number of events in the control group divided by the total number of patients in the control groups. In this example, it would be 594/1066 = 557 out of 1000. Automatic calculations in GRADEpro

• 2. present the median control group risk from the studies included in a meta‐analysis. This is automatically calculated

by GRADEpro and is the “medium risk”.

• 3. present up to 3 risks based on the control group risks in the studies included in the meta‐analysis. You can calculate

a low, medium and high assumed risk from the studies. Alternatively, for a high and low risk population you can choose the second highest and second lowest control group risks in the included studies.

• 4. present a baseline risk from observational studies. You may enter a low, medium, or high risk.

Calculate the corresponding risk Risk Ratio: The assumed risk is multiplied by the Risk Ratio; the confidence intervals are calculated in the same way. Relative Risk (0.93) X 649 = 604 Lower confidence interval (0.85) X 649 = 552 Upper confidence interval (1.02) X 649 = 662

Study or Subgroup Lebeau 1994 Altinbas 2004 Agnelli 2009 Weber 2008 Klerk 2005 Sideras 2006 Perry 2010 Kakkar 2004 Total (95% CI) Total events Heterogeneity: Tau² = 0.01; Chi² = 10.75, df = 7 (P = 0.15); I² = 35% Test for overall effect: Z = 1.57 (P = 0.12) Events 96 22 333 8 88 40 45 103 735 Total 138 42 769 10 148 68 99 190 1464 Events 110 30 155 10 107 41 32 109 594 Total 139 42 381 10 154 69 87 184 1066 Weight 20.6% 6.1% 19.7% 6.1% 16.9% 8.6% 6.0% 16.0% 100.0% M-H, Random, 95% CI 0.88 [0.76, 1.01] 0.73 [0.52, 1.04] 1.06 [0.92, 1.23] 0.81 [0.57, 1.14] 0.86 [0.72, 1.01] 0.99 [0.75, 1.31] 1.24 [0.87, 1.75] 0.92 [0.77, 1.09] 0.93 [0.85, 1.02] Heparin Control Risk Ratio Risk Ratio M-H, Random, 95% CI 0.5 0.7 1 1.5 2 Favours heparin Favours control

Median risk calculated by GRADEpro from meta‐analysis

Medium risk population RR 0.93 (0.85 to 1.02) 649 per 1000 604 per 1000 (552 to 662)

Odds Ratio: OR is first converted to RR. Then calculated as a risk ratio as above.

)) 1 ( ( 1 OR R OR RR

A

   

where RA is the assumed risk. Hazard Ratios and Rate Ratios can also be converted. See the HELP file in GRADEpro or the Cochrane Handbook (Chapter 11 ) for more information about these conversions. Presentation of a CONTINUOUS OUTCOME (Mean difference) Example: Quality of life score when people with chronic obstructive pulmonary disease participate in a self‐management programme versus when they receive usual care

Outcomes Illustrative comparative risks* (95% CI) Relative effect (95% CI) No of Participants (studies) Quality of the evidence (GRADE) Comments Assumed risk usual care Corresponding risk self management Quality of Life St George's Respiratory Questionnaire. Scale from: 0 to 100. (follow‐up: 3‐12 months) The mean quality of life ranged across control groups from 38 to 60 points The mean quality of Life in the intervention groups was 2.58 lower (5.14 to 0.02 lower) 698 (7)



moderate Lower score indicates better quality of life. A change of less than 4 points is not shown to be important to patients.

Determine the assumed risk Determine the range of scores at end of study in the control group. From the meta‐analysis in the example, it ranges from 38 to 60. Determine the corresponding risk The corresponding risk does not need to be calculated. It is the mean difference from the meta‐analysis. It essentially means that the quality of life score when people participated in the self management programme was 2.58 points (5.14 to 0.02) lower than when they received usual care. Standardised Mean Differences can also be presented. There are a number of options for presentation. See the HELP file in GRADEpro or the Cochrane Handbook (Chapter 11 ) for more information about these calculations.

Study or Subgroup Bourbeau 2003 Boxall 2005 Coultas 2005a Coultas 2005b Gallefoss 1999a Monninkhof 2003 Watson 1997 Total (95% CI) Heterogeneity: Chi² = 4.72, df = 6 (P = 0.58); I² = 0% Test for overall effect: Z = 1.98 (P = 0.05) Mean 50.6 50.7 58.6 55.1 40 37.4 39 SD 17.8 11.8 20.4 16.4 16 18.8 17 Total 81 23 49 51 26 122 29 381 Mean 54.2 59.6 58.8 58.8 43.1 37.7 39 SD 17.6 13.3 16.4 16.4 21 17 16 Total 76 23 26 25 27 113 27 317 Weight 21.4% 12.4% 9.1% 10.6% 6.5% 31.3% 8.8% 100.0% IV, Fixed, 95% CI

• 3.60 [-9.14, 1.94]
• 8.90 [-16.17, -1.63]
• 0.20 [-8.71, 8.31]
• 3.70 [-11.55, 4.15]
• 3.10 [-13.13, 6.93]
• 0.30 [-4.88, 4.28]

0.00 [-8.64, 8.64]

• 2.58 [-5.14, -0.02]

Treatment Control Mean Difference Mean Difference IV, Fixed, 95% CI

• 10
• 5

5 10 Favours treatment Favours control Mean 54.2 59.6 58.8 58.8 43.1 37.7 39 SD 17.6 13.3 16.4 16.4 21 17 16 Total 76 23 26 25 27 113 27 Control