| Value | Category | 
                                    
                    
                        | 1 | Scar present | 
                                    
                    
                        | 2 | Scar not present | 
                                    
                    
                        | 3 | Unsure if scar is present | 
                                    
                    
                        | 7 | Not checked | 
                                    
                    
                        | 9 | Missing | 
                                    
                    
                        | Sysmiss |  | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.