Interfaces Abound

It is fun to think that there is one central hospital health information system (HIS); however, in reality, most organizations have a vast number of information products that connect to that HIS.  One of the most common interfaces is the admission/discharge/transfer (ADT) interface.  Most HIS systems use the HL7 standard to share information among third party systems. Once, I asked the interface engineers just how many interfaces they supported and was surprised to learn that there were hundreds of interfaces. This figure included the inbound, outbound, and bi-directional interfaces. Note that many systems have more than one interface. In my previous blog, I mentioned that an ADT interface had stopped working and the users had implemented an unexpected user work around. I was curious as to why the interface engineers didn’t realize that there was a problem and, instead, relied on the users to report the failure.  I suspected that, if you looked at the interface transaction log, you would be able to see that there was a problem. 

Generally, when you send an electronic message, there is an acknowledgement sent back from the receiving system. This information is stored in “log files.” So, how did we miss the failure of the ADT interface? Given that there are hundreds of interfaces and thousands of messages going back and forth, one can begin to understand how the log files containing the error messages were missed. I wondered if there was a seminal event that should have flagged an interface log review.  In wanting to understand the interface failure, I reviewed the logs and found that the errors began when the organization accepted a HIS software update. Along with the software update, the organization had made two small changes to the data format of two data fields. One change was to the unique patient identifier and the other the patient location code. One change involved expanding the cost center structure from four characters to six.  The second involved changing the data format for the patient identification number to include alpha characters; the number was previously exclusively numeric characters.  Once the HIS software update occurred, the ADT interface to the HIS failed.  Some ideas that would be helpful in this situation and similar ones, include:

·         Test interfaces after system updates are rolled out and before go-live

·         Predict potential failures knowing  that computers are very literal and follow parameters exactly as prescribed (e.g.,  data fields have prescribed data formats and changes to data formats suggest that changes to data field configuration might also be necessary)

·         Check with the interfaced product users post go-live to assess if there were any unforeseen impacts 

·         Monitor interface logs post go-live for error messages

Once we realized the interface failure occurred, the fix was quick.  Our investigation revealed two issues:   a) a reject message indicating the six character cost center did not exist, and b) a truncation of the patient identification number that removed the alpha character.

Lesson Learned: Changes to data format and structure may break interfaces.