| Value | Category | 
|---|---|
| 1 | Blood taken - and valid result obtained | 
| 2 | Not present | 
| 3 | Refused | 
| 4 | Originally 'Blood taken', but no barcode in questionnaire | 
| 5 | Originally 'Blood taken', but no corresponding barcode at lab | 
| 6 | other | 
| 8 | Nagaland: information not collected |