PDS API Patient search returns unexpected match

Personal Demographics Service (PDS) Personal Demographics Service FHIR API
1

Using the PDS API against the INT environment, we have found that the returned results don’t always match the search parameters.

Searching for a patient with these parameters:

{
  birthdate: '2011-05-09',
  gender: 'female',
  family: 'Shipperbottom'
}

returns a Bundle containing a single matched Patient resource with these attributes:

{
  birthdate: '1926-09-24',
  gender: 'male',
  family: 'Shipperbottom'
}

We expected that the matched Patient resource would be consistent with the search parameters.

Why does the service return this result?

2

Having done some further investigation, we can see that this problem occurs for around of the first patients listed in the PDS test data spreadsheet so we can confirm that this is not an isolated problem with a single patient.

The following combinations of parameters exhibit the problem:

           {
              birthdate: '1943-05-19',
              gender: PatientGenderCodes.FEMALE,
              family: 'AINDOW'
            },
            {
              birthdate: '2011-05-09',
              gender: PatientGenderCodes.FEMALE,
              family: 'SHIPPERBOTTOM'
            },
            {
              birthdate: '2009-02-15',
              gender: PatientGenderCodes.MALE,
              family: 'ANDERTON'
            },
            {
              birthdate: '2008-05-21',
              gender: PatientGenderCodes.MALE,
              family: 'FIELDING'
            },
            {
              birthdate: '2001-01-26',
              gender: PatientGenderCodes.FEMALE,
              family: 'SEO'
            }
3

Some background:
For “simple” searches, PDS uses inverted indexes, these are usually updated when a pdsRecord is saved.
It looks like, in the case of these particular records, the way they’ve been loaded has not updated those indexes and we’ve been left with some stale entries.
I’m investigating as to the tool used and will recommend we add some improvements to prevent this happening in future. I’ll also look to clear out the aforementioned stale indexes for these records.

This will not happen in live as we do not use these tools to load test data.

2 Likes
4

Thanks for this update - it’s always useful to understand the system architecture.

For our hazard log entry, the same problem could occur in production but the risk is mitigated through operational controls (i.e. not using test tooling to load data) and the probability of occurrence will be very low. For our use case I don’t think we’ll then need to add any further mitigation.

5

We’ve retested this following the fix and find that searching for a patient with these parameters taken from the All PDS Data dataset no longer returns any matches:

{
  birthdate: '2011-05-09',
  gender: 'female',
  family: 'Shipperbottom'
}

We can retrieve a patient by searching using these parameters (i.e. the values previously returned as an erroneous response):

{
  birthdate: '1926-09-24',
  gender: 'male',
  family: 'Shipperbottom'
}

The returned patient has NHS Number 9449306621, but has materially different demographics than for this patient in the test dataset.

Is it expected that the INT system contains different patients to the All PDS data test cases?

6

NHS API Management team let me know that the INT system should be consistent with the test pack. They haven’t provided any information about if/when this will be resolved.

7

Tested again and the problem is still present.