Urine hCG on the Clinitek Status +

Looking into discrepant urine hCG results on our Clinitek Status + analyzers in our Emergency Room...

We had one false negative on a women in which fetal heartbeats were detected. Urine hCG in lab was positive. Quantitative hCG was >10,000.

About a week later we had two false positives. Patient 1 had a positive hCG in the ER on Saturday. She called back to state she had taken 3 at home pregnancy tests and all were negative. Returned to ER today and both urine hCG and quantitative hCG were negative. Patient 2 also had a positive urine hCG in ER. At that time they were questioning the validity of the results so they sent it to lab and it was negative.

I'm thinking this might be a cassette lot issue. Anyone have any suggestions? Siemens is essentially saying it is user error, which I question.

Replies to this Topic

I have not had issues with false negatives (thankfully) - your first example, I would be suspicious of user error, or possibly hook effect?

I HAVE had issues with false positives - usually a borderline result, but occasionally an actual positive.  Of course with them being done POCT, it was always difficult to actually retrieve the developed cartridge, but sometimes I was able to.  In at least one case, I could visually see the "line" indicating a positive test, so it wasn't like the instrument was seeing something that wasn't there (serum hCG on the patient was negative).  So yes, I also believed my problem to be lot/cartridge related, or an interfering substance in the patient's urine.  Ran 10 positive and 10 negative QC just to re-verify performance - no errors.  Siemens did not concur that it was cartridge-related and insisted on replacing the analyzer, which we did.  I have since instituted a policy whereby they are to repeat all borderline uCG results, and also emphasized (again) not to test bloody or intensely-colored samples.  That was about a year ago, and I have not had the problem reoccur to my knowledge.  But if the machine has to "err" on one side, I would certainly rather it be false positives rather than negatives.

Edited Tue, Sep 12, 2017 5:46 PM

I also had false positives recently /

The urine was mucoid.

We had issues in the past and decided to drop the Clinitek test and go with a kit.

We recently had false positive results in the ED. When the POC department went to investigate/troubleshoot the negative control resulted as positive. The calibration bar was dirty.

Interesting, Cristie.  I have my users wiping down the calibration bar once weekly and I still had my problems.  Unless of course they're telling me they're doing it and they're not actually doing it :).   But, glad to hear it was attributable to something that can be controlled.

No negative QC failures?

Our QC has been fine. I personally repeated one of the false positives and it came back positive for me on two different lots of cassettes.

This is scaring me!  We are implementing the use of the Clinitest in our ED next week.  I think the false negative result could be attributed to the Hook effect.  The false positives have me worried.

I considered the hook effect for the false negative, but the Clinitest package insert states: "High-dose hook effects are not seen with this product until the urine hCG level exceeds 600,000 mIU/mL, a level two to three times higher than the highest level seen for pregnant individuals."

Steven Lee - I would not let that discourage you from using the Clinitek STATUS from an overall quality perspective.  Even with the occasional problem (false positive), I would still prefer to have an analyzer making the interpretation of a POCT test as opposed to a visual read on a kit.  And from a POCT compliance perspective, there are so many issues that are automatically assured, like having untrained operators locked out, QC lockouts, and internal QC consistently interpreted with each patient test.  Plus, having every patient test accountable because the results are interfaced, unlike a kit method where there are tests done that you have no way of tracking because the users fail to document or document incompletely.  All the things you need because it's the wild west when the test is taken out of the lab.  It's really quite a no-brainer, in my opinion.



It may indeed be the hook effect above 600,000 mIU.

On your quantitative instrument the result was >10,000

This probably means the analyzer cant accurately produce results over 10,000 to give a precise # so it results in >10,000. If you still have the sample I would dilute it with a known negative sample and see if it is over 600,000. As you mentioned a fetal heart beat was detected, I bet their hCG was off the charts.

Edited Thu, Sep 14, 2017 11:08 AM

Good catch, Dave.


The actual hCG quantitative was 99,000, well below the 600,000 cut off that the company reports the hook effect takes place at with their test cassettes.

We met with Siemens to discuss the false negative and false positive results. We were told that there could be an invisible fingernail scratch on the white bar on the test table and that could cause discrepant results. When we inquired why our QC would still be acceptable, they stated they didn't know. Siemens did nothing to reassure of us their instrument or test cassettes.


Great you checked. Now the next question is what reference analyzer are you using? Some check more hcg variants than others. If indeed a invisible fingernail scratch, did you try a new table with the white bar if you still have the sample. Maybe they can get you one since its scratched?

We tried a new test table and all results were fine, so I am quite sure it is the test table. We are past the point of troubleshooting. We will not be using this analyzer because the instrument and/or QC does not notify the user or indicate when there is an "invisible scratch" on the test table that could cause discrepant results.

I'm really surprised the test table isn't checked during an instrument self check with every test. The maintenance was performed regularly as recommended by the manufacturer. The sales people told us that it is just the recommended frequency but that we should do it more frequently. But honestly, if even your QC passes when there are test table issues, how could you ever be sure of your results? Overall Siemens was not helpful at all. They sent two sales people. I miss my old rep, she was the best.  

Melissa - did they suggest a power-off/power-on periodically?  Because it does do a self-check when it is powered-off, then on.  I wonder if this issue might be caught then.


This is quite disturbing as there aren't many automated uCG readers out there.  Even more disturbing that Siemens didn't have more solutions for you.

I have my users cleaning the calibration bar weekly in the interest of AVOIDING this problem; wondering now if I am doing more harm than good!

James - in my investigation the instrument was powered off and on multiple times and never produced an error code or anything to indicate that there was something wrong with the test table. We also cleaned the calibration bar weekly and let it air dry as recommended. Unfortunately, cleaning weekly did not prevent our discrepant results. The test table was cleaned 5 days before our discrepant results were discovered.

Anyone have any suggestions on alternatives? Definitely on the market for a new platform!

Melissa - There is a new rapid blood-based hCG lateral flow test on the market today produced by a company called NOWDiagnostics. If you are interested, my email is morgan.peterson@nowdx.com and I would be happy to share more information with you. The test operates on a few drops of blood (capillary/or venous whole blood, plasma, or serum) so it will not be susceptible to false positive or negatives in the way that urine tests are. It also detects pregnancy down to 10 mIU/mL. 

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