How to tell if a segment actually exists in a HL7 message via NHAPI?

Question

I have an SIU S12 message that does not contain a PV2 segment. However, when I get the parsed message from NHAPI, the parent group for PV2, the SIU_S12_PATIENT group, return 1 for currentReps ("PV2"), which means the PV2 is present.

var parser = new NHapi.Base.Parser.PipeParser();
var parsedMessage = parser.Parse(message) as NHapi.Model.V231.Message.SIU_S12;
var patientGroup=parsedMessage.GetPATIENT(0);
// This call should not create the segment if it does not exist
int pv2Count=patientGroup.currentReps("PV2");
//pv2Count is 1 here despite no PV2 segment exists in the message
//also Both GetAll("PV2") and SegmentFinder say the PV2 segment is present
//DG1RepetitionsUsed is also 1 despite no DG1 segment is present in the message

I am trying to avoid writing code to evaluate every field in the segment. PV2 is just an example - there are a lot more segments that could be missing from the message source.

I am using NHAPI v 2.4, the latest version.

Update: following Tyson's suggestion I come up with this method；

var parser = new NHapi.Base.Parser.PipeParser();
var parsedMessage = parser.Parse(message) as NHapi.Model.V231.Message.SIU_S12;
var encodingChars = new NHapi.Base.Parser.EncodingCharacters('|', null);
var patientGroup = parsedMessage.GetPATIENT(0);
var dg1 = (NHapi.Model.V231.Segment.DG1) (patientGroup.GetStructure("DG1"));
string encodedDg1 = NHapi.Base.Parser.PipeParser.Encode(dg1, encodingChars);
bool dg1Exists = string.Compare(encodedDg1, 
    "DG1", StringComparison.InvariantCultureIgnoreCase)==0;

Tyson Moncrief · Accepted Answer · 2013-07-11T21:33:29.287

easiest thing that I have found to do is to determine if a segment is in a message is to search the actual string of the message for the segment name plus a pipe. So, for example

    if(message.Contains("PV2|"))
    {
        //do something neat

    }

From my experience, it is either that, or examining every sub-field under the segment to see if there is a value.

EDIT

I found another way to check that might work a little better. The PipeParser class has a couple of static methods on it that takes in ISegment, IGroup, and IType objects that will return a string representation of the object NHapi reference.

Sample code:

        string validTestMessages =
      "MSH|^~\\&|ADT1|MCM|LABADT|MCM|198808181126|SECURITY|ADT^A01|MSG00001|P|2.6\r" +
      "EVN|A01-|198808181123\r" +
      "PID|||PID1234^5^M11^HBOC^CPI^HV||JONES^WILLIAM^A^III||19610615000000|M||2106-3|1200 N ELM STREET^^GREENSBORO^NC^27401-1020|GL||||S||S|123456789|9-87654^NC\r" +
      "PV1|1|I|||||TEST^TEST^TEST||||||||||||||||||||||||||||||||||||||||||||\r";

        var encodingChars = new EncodingCharacters('|', null);

        PipeParser parser = new PipeParser();

        var message = parser.Parse(validTestMessages);

        PV1 pv1 = (PV1)message.GetStructure("PV1");
        var doctor = pv1.GetAttendingDoctor(0);


        string encodedMessage = PipeParser.Encode(pv1, encodingChars);
        Console.WriteLine(encodedMessage);

        encodedMessage = PipeParser.Encode(doctor, encodingChars);
        Console.WriteLine(encodedMessage);

Output:

PV1|1|I|||||TEST^TEST^TEST
TEST^TEST^TEST

if there is no segment or the item is empty, then the PiperParser will return an empty string.

the PiperParser does not return an empty string but returns the segment name. But that can still be used to check if the segment is empty, thanks. — Sheng Jiang 蒋晟, Jul 12 '13 at 22:18

Ranvijay Sachan · Answer 2 · 2014-07-02T09:44:26.063

You can read segment line by line to a file and add in hl7 Record object and check segment exist or not.

package com.sachan.ranvijay@gmail.com.hl7.msg;

    import java.io.BufferedReader;
    import java.io.File;
    import java.io.FileReader;
    import org.nule.lighthl7lib.hl7.Hl7Record;
    import org.nule.lighthl7lib.hl7.Hl7Segment;
    import com.stpl.hl7.dto.HL7PatientInfoDTO;

    /**
     * This class will parse the hl7 message. it can accept message  file in the format of java.io.file
     * as well as String. Its Uses org.nule.lighthl7lib.hl7.Hl7Record 
     * as a main component.
     * @author Ranvijay.Singh
     *
     */
    public class PrepareHL7Message {
        StringBuilder hl7Msg = new StringBuilder();
        Hl7Record record = null;
        public PrepareHL7Message(File file) throws Exception {

            BufferedReader reader = new BufferedReader(
                    new FileReader(file));
            String str = reader.readLine();
            while (str != null) {
                hl7Msg.append(str).append("\r");
                str = reader.readLine();
            }
            reader.close();
            try{
             record = new Hl7Record(hl7Msg.toString());
            }catch (Exception e) {
                throw e; 
            }
        }

        public PrepareHL7Message(String msg) throws Exception {

            try{
             record = new Hl7Record(msg);
            }catch (Exception e) {
                throw e; 
            }
        }
    private HL7PatientInfoDTO getPatientOrderingPhysician(HL7PatientInfoDTO padto) {
        Hl7Segment seg = record.getSegment("PV1");
        if(seg!=null)
        padto.setOrderingPhysician(seg.field(7).toString());
        return padto;
    }
    }

//DTO.............

package com.sachan.ranvijay@gmail.com.hl7.dto;

public class HL7PatientInfoDTO {

    /**
     * maped with PV1-7
     */
    private String orderingPhysician;

    /**
     * @return the orderingPhysician
     */
    public String getOrderingPhysician() {
        return orderingPhysician;
    }

    /**
     * @param orderingPhysician the orderingPhysician to set
     */
    public void setOrderingPhysician(String orderingPhysician) {
        this.orderingPhysician = orderingPhysician;
    }
}

How to tell if a segment actually exists in a HL7 message via NHAPI?

2 Answers2