Passing variable into AJAX success

Question

Here's the basic idea with my code. I added comments where I'm having issues. Basically, I need to get the value from a select (no problem) and pass this into an AJAX query to be used in both the query (no problem) and in the success (the issue).

var picked_dis;
$(document).ready(function() {
$('#disease').change(function(event) {

     picked_dis = $('#disease').val();

    $.ajax({
        url: 'https://something.cartodb.com/api/v2/sql?q=SELECT territory,'+picked_dis+' from testnumbers_merge', 
//variable works in the above

        type: 'GET',
        success: function(data) {
            var ticks6 = data.rows.map(function(ele) {
                return ele.picked_dis; //this is where I want the variable to work but doesn't

            });
         console.log(picked_dis);//this returns the correct variable
            ticks6.sort(function(a, b) {
                return a - b
            });
  });
 });
 });