/**
  * Get observation identifier
  *
  * @param DOMNode            $node   DOM node
  * @param CObservationResult $result Result
  *
  * @return string
  */
 function getObservationIdentifier(DOMNode $node, CObservationResult $result)
 {
     $identifier = $this->queryTextNode("OBX.3/CE.1", $node);
     $text = $this->queryTextNode("OBX.3/CE.2", $node);
     $coding_system = $this->queryTextNode("OBX.3/CE.3", $node);
     $value_type = new CObservationValueType();
     $result->value_type_id = $value_type->loadMatch($identifier, $coding_system, $text);
 }