Accuracy of blood test results varies

Accuracy of blood test results varies

With a CLL diagnosis, many of us change from our earlier experience of being blithely ignorant of our blood test results, to taking an arguably unhealthy interest regarding each blood test, often worrying unnecessarily due to variations which are of no consequence.  I know I certainly took a few years to get comfortable with seeing lots of out of range results and a growing ALC until I became familiar with the new norm for someone with CLL.  In answering questions others have posed, I've often pointed out that there is an inherent reproducibility limitation in measuring blood counts.  This means that it is quite possible to get several apparently quite different results, perhaps even showing an apparent trend, while each of the apparent different results is within the accepted natural variation possible when machine counting the same sample.

From The Hematology Times (free registration):

"A comparison of commercially available blood tests has revealed more variability than expected, according to researchers.

The group compared basic blood tests run by commercial laboratories and found the testing service, type of test, and time of collection all influenced the accuracy of results.


The researchers collected peripheral blood samples from 60 healthy adults at 4 separate time points within a 6.5-hour window. The samples were collected in Phoenix, Arizona, at an ambulatory clinic and at retail outlets with point-of-care services.



More than half of the test results showed significant differences between test providers. Of the 22 tests, 15 (68%) showed significant variability between labs.


Triglyceride levels and red blood cell counts were among the most consistent results, while white blood cell counts and overall cholesterol levels were among the most variable. (My emphasis - Neil)


In addition, the researchers noted that, although they controlled subjects’ eating and physical activity, data from blood samples collected earlier in the day were sometimes significantly different from samples taken from the same subjects later in the day."

This is why you should minimise other sources of variation in your blood test results by always using the same pathology service, having your blood sample taken around the same time of the day and also following the same daily living pattern prior to your blood test.


Photo:  Speaking of punctures, an Echidna (Australia's spiny ant-eater) hunting for food that I was delighted to photograph a few weeks ago.  Echidnas lay eggs and suckle their young.  If you get too close to one, it will quickly dig into the ground with those powerful legs and leave just those formidable spines exposed.  Run over one and you have to throw your tyre away - those spines keep working their way through the tyre.  Doesn't do the echidna much good either... 

Last edited by

12 Replies

  • This strikes a cord with me Neil. Within the space of 10 months, I have gone from ignorant bliss to feverishly examining and comparing every little change and back to a comfortable state of watching but not going mad. I am sure  that as the CLL progresses I will again experience all three of these emotions!

    However, I'm a girl who would rather worry about what I know than what I Don't know so will still scan my results each and every time for any changes.

    I will however try to go at the same time of day, I can see that makes sense.

    Thanks Neil, your input is always so valuable


  • Who wouldn't be pleased to photograph a echidna at such close range. Lovely photo. Also liked the Wren yesterday. In the UK the wrens are brown with shorter tails  and along with the Robin my favorite birds.Thanksm

  • Thanks to this site I am always keen to see my blood test results. It's good to understand how you are doing. Just my opinion.

  • Part 3/ struggling a bit to get the keyboard to stay, and when I try to edit it's a job to get it to come back. Will monitor it forva while. This is why the message is in three pieces.

    Thanks sue.

  • I've still got the same problem with the keyboard and editing Sue. 


  • Thanks Newdawn for letting me know.


  • Have you both done a FORCED update of the HU webpage as recommended by HU to update the text handling script on your devices for this site?

  • I thought I had . will continue to monitor.sue

  • Interesting point about the pathology service. I'm due to move house at the end of the month so after ten years at the same service I'll be under a new one. Have to look out for any variations. 

  • This is long. If you need sleep, or like this sorta thing, read on.

    I am fascinated by this sort of study. Having worked as an IT person in a hospital lab, I can assure everyone that despite all of the computer technology, the problems with lab results are generally due to human error and ignored assumptions. 

    For those who also want to geek the topic to the max, here is the original journal article:

    My favorite thing to note about routine blood tests is that there is almost no control for temperature during shipping in the U.S. Everyone just assumes that it's all done properly - no temperature measurement is taken. This keeps costs down a wee bit. The regulations outside of the U.S. may differ, however.  Note that the study was conducted for the most part in Phoeniz, Az, in July, where average daytime temperatures often exceed 38C (100F). 

    So I decided to geek the temperature control of routine CBC shipments.

    Here's what Quest says about shipping lavender tubes for CBCs:

    They expect room temperature, which they define elsewhere as 15 - 30°C. What guarantees that? If the package is sent by UPS or FedEx, the shipper must pay for special temperature treatment:

    FedEx offers a Clinical Pak to assure physical safety from breakage of the sample - but temperature control is a separate service: 

    UPS has something they call Temperature True, but their Temperature True Standard appears to focus only on delivert time:

    In the past, I have not seen anything on shipping packaging to indicate that this sort of temperature controlled shipping is used. The packaging is generally only to prevent breakage. I will check again on my next visit to the clinic, and report back.

    Scientists have studied the effects of packaging and ambient temperature on blood samples. The study below indicates that despite typical expectation of room temperature, samples are often exposed to extremes:

    "Shipments of patients' blood specimens were continuously monitored using the TempCheck Sensor (Marathon Products, Inc., San Leandro, CA) to determine the temperature range to which blood samples were exposed when shipped overnight by commercial carrier, and to evaluate the effects of those temperatures on cell yield."

    Fig. 7 shows that even with thermal packaging, temperature of the sample exceeded 30C after exposure to ambient 45C after 15 hours. 

    My conclusions:

    Most of the time, your samples are probably safe from temperature extremes if thermal packaging is used, and total time from clinc to lab shipping time is less than 15 hours. I imagine that most of that time is spent at the clinic, in a shipping warehouse, or the lab itself. The truck (lorry) or aircraft should be only a few hours, but it's really hard to tell.  Most clinics I've been to do a single pickup at the end of the day. A morning draw sits inside the clinic till then.

    My Quest results show both the difference in time between when the sample was drawn and when it was received by quest were generally 12-18 hours, usually arriving in the wee hours after a trip on a plane and trucks at each end. 

    My insurance now demands LabCorp. and I've only used them twice, so far. LabCorp does not report the time they received the sample.. The report times were 8.5 and 23 hours from the sample time. 

    Even without the temperature extremes, lab results are fuzzy numbers. There is a tolerance range of error for the instrument - and it's not often disclosed.  Changing labs can make a small difference. Changing the type of container the blood goes in probably changes a lot more things than anyone expected.

    I plan to check if my samples are sent with temperature monitoring, and what sort of packaging.

  • Any thoughts on how draws done at hospital labs compares with "regular" blood labs? 

  • I'd say it depends on whether the hospital has its own on-site service and how well maintained that is.  One hospital I stayed in had such a service and my interim blood test results were promptly available as well as the final, adjusted results somewhat later.  Another stay at a smaller hospital resulted in my blood sample being sent off to a distant pathology service and the results took some time to be processed.  Not surprisingly, they were reported as mildly haemolysed (ruptured red blood cells release their contents into the blood plasma, which can be due to specimen collection, processing, or most likely transport)

    That report clearly stated that 'unreliable results may occur for potassium, phosphate, AST and LDH'.  My LDH result (which in CLL provides an indication of how active the CLL Is and also can jump to multiple normal levels with Richters) was the highest I've recorded at double normal, but I at least knew not to be too worried!


You may also like...