Blank Serial Print AdaFruit BTLE I working on a prototype with an Arduino UNO and an AdaFruit Low Energy Blue tooth

I have an array of uint32_t that I am trying to send via blue tooth to a given device.  I don't think i can send the array so I was trying to send it as a comma separated string. 

I can print out each individual index of that array just fine, but its completely blank when i try to make a comma separated String..  See code and comments below.

Ay Array:

uint32_t items[]= {0,3513728,7925384,0,0,0};


In My Loop:

String output = "";

for(int i = 0; i&lt;6;  i++){

  BTLEserial.print(items[i]); // Prints as expected
  output += getStringForUI32_T(items[i]);
  output+=",";

 }
 BTLEserial.print(output); // prints BLANK


I imagine this has something to do with memory but I am at a complete loss.. Please help!
I'd probably do it directly like:

for(int i = 0; i&lt;6;  i++) {
  BTLEserial.print(items[i]);
  BTLEserial.print(',');
}
BTLEserial.println();


But with the string I think it would be something like:

String output = "";

for(int i = 0; i&lt;6;  i++) {
  output += getStringForUI32_T(items[i]);
  output+=",";
}
BTLEserial.println(output[0]);


But as someone else got it working using String on your adafruit thread maybe this is just barking up the wrong tree.