Many thanks Steve for this preliminary data. It is an important data set which will help quantify his potential issue. It  gives us  the context within which we can recommend
a way of handling AKI warning stage test results in pregnancy.

Dr Robert Hill
Consultant Clinical Biochemist
________________________________________
From: ACB AKI-Detection-Algorithm [[log in to unmask]] On Behalf Of Steve Holding [[log in to unmask]]
Sent: 03 August 2015 15:26
To: [log in to unmask]
Subject: Creatinine requests within 1 year of pregnancy

A little while ago there was a query on the list about how many patients have a creatinine performed within one year of pregnancy.
This related to the risk of false positive eAKI alerts as a result of the low creatinines seen in pregnancy.

I've managed to trawl through our data to see how much of a problem this might be:

I identified all patients having a Down's screen over one year and extracted the NHS number and gestation in days.
These anonymised data were used to count the number of creatinines done between LMP and EDD (calculated from the gestation based on ultrasound scan), and also the number of tests done in the year following EDD.

I then counted how many patients fall into both groups. I.E. had a test done between LMP and EDD, and one done in the year after EDD.
I'm currently trying to work out a more systematic way of checking the data for false positive AKI alerts.
But, the results so far show:

3523 Patients
2988 tests (1343 patients) done between LMP and EDD
2337 tests (1182 patients) done between EDD and 1 yr post EDD
595 patients in both groups.
This will be an overestimate of the number of patients affected because the period covered is in effect 21 months, not 12.

I.E. 17% of patients had a test during pregnancy and within the year following pregnancy. The distribution of when after EDD these tests were done peaks in the first month (20% of requests) and is then flat for the rest of the year (5-8% per month)

Taking the latest sample during pregnancy and pairing it with the earliest sample after EDD but at least 14 days post EDD and with less than 365 days gap, there were 50 patients that had an increase in creatinine of more than 50% and so would have triggered the eAKI alert (1.4% of pregnancies). This will underestimate the true number. The distribution of creatinine values in this group looks like the normal reference distribution apart from one patient with creatinine of 1500.

So..... a lot of creatinines being done in this period but probably relatively few false positive eAKIs generated.
I'd be interested to hear you comments.

Steve Holding
Consultant Clinical Scientist
Hull Royal Infirmary


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