Clinical Trials

❘❙❚■ Chapter 35 | Use of TablesSpecific information for fields of tablesAsterisksP-values can sometimes be quoted using asterisks to indicate levels of significance,eg, in a larger table where quoting the P-values themselves would lead to acumbersome table. The normal convention is to use * for P < 0.05, ** for P < 0.01,and *** for P < 0.001, for those values achieving statistical significance [9].Blank cellsAlways fill in blank cells, with zeros if appropriate, or with a note to say why thedata is not available. If you use the abbreviation ‘NA’, state whether this refers to‘not available’ or ‘not applicable’ [8]. If a large number of fields contain zerosor no information, this can be considered a waste of space and you need toconsider restructuring the table or including the information in a different way(eg, combine some rows together).Note on deducing statistical significance fromconfidence intervalsTo deduce significance from a CI on a ‘statistic of comparison’, look to see whetherthe CI contains values that indicate there is no difference between the groups beingcompared. For example, does a 95% CI on an odds ratio, hazard ratio, or relativerisk contain the value 1.0 within the range given? If so, then the results areconsistent with there being no statistically significant difference between the twogroups and we can deduce that P will be greater than 0.05. If the entire 95% CI isabove (or below) 1.0 then there is evidence that there is a significant differencebetween treatment groups with respect to this outcome measure and P will be lessthan 0.05. Similarly, if a 95% CI for an estimated absolute difference in outcomesbetween treatments contains the value 0 (ie, the lower limit is negative and theupper limit is positive) then P > 0.05; otherwise, if the CI contains only positive oronly negative values then P < 0.05 (see Chapter 18).Finally, it is important is to make sure that:• all the key results are contained within the report• written interpretations are consistent with the tables• repetition between tables and text is minimal404