For those that don’t know me, I'm Chris. I’ve worked as a Senior Biomedical Scientist within a big UK NHS lab for over a decade. Often the behind the scenes of the labs is a bit of a mystery to patients and even doctors and nurses - and yet, we are responsible for over 70% of diagnosis.

So here, I'm going to teach (and show) you a little of that behind the scenes. Where do your samples go?

There are several key tests that help doctors to diagnose and monitor IBD patients.

💩 Faecal Calprotectin — What It Actually Tells Us

I love this test. You know why? Because it's a success story for the NHS and IBD patients. Despite the biomarker being identified in the early 1990s, it was a large push for NHS labs to prove its value before its routine adoption in 2015 - 2018.

When I was first diagnosed in 2013, it wasn’t available. And that led to being prodded to no end, before a colonoscopy was finally performed and I got my UC diagnosis. Now it is a routine screen to diagnose IBD and monitor flares.

What it is: Calprotectin is a protein released by neutrophils (a type of white blood cell) when there’s inflammation in the gut. The more inflammation, the more calprotectin ends up in the stool.

Why it matters: It’s a non-invasive biomarker of intestinal inflammation — meaning it can help tell the difference between IBD (inflammatory) and IBS (non-inflammatory) conditions without needing a camera up either end 🙏 - that’ll come later ha!

💩 My Tips for Collecting a Stool Sample (for Calprotectin) for the most Accurate results:

You only need a tiny amount!
Around a pea-sized portion (50–100 mg) is enough. Patients often send far more than the lab needs — but it’s the quality, not the quantity, that matters.

Use the right container. Always use the calprotectin kit or pot provided by your GP or hospital. Some use special spooned lids or collection sticks built into the cap.

You would be surprised by some of the containers people send their samples in. True story: I once received a full poo inside a morrisons shopping bag….Please dont do that!!!

Take the sample from a representative area.

• If the stool looks normal, take it from the middle rather than the surface — it gives a more accurate result.
• If the stool is loose or mixed with mucus, just collect a small portion that looks typical of your overall movement.
• Avoid visible blood or large amounts of mucus, if possible — they can artificially elevate the result or cause inconsistent readings.

Keep it clean. Try to avoid sample contamination with urine, toilet water, or cleaning products. Some people find it easier to use plastic wrap or a clean disposable container in the toilet bowl to catch the sample.

Label it clearly and get it to the lab promptly. (We can’t accept it, if there are spelling mistakes or not enough identifiers - our lab needs Forename, surname, DOB, and NHS/hospital number. Faecal calprotectin is fairly stable, but best practice is to deliver it within 24–48 hours. If you can’t, store the pot in the fridge (not freezer) until you can drop it off.

Timing doesn’t need to be exact. There’s no strict fasting or timing requirement — just try to collect a sample during a period when your bowel symptoms reflect how you’ve been feeling (not after one unusual day).

🩸Full blood count. This one’s my baby since I specialised in hematology.

We use an analyser called the Sysmex XN (best in the biz) - each capable of running 100 samples an hour, and we have 6 of them all on a giant scalextric (for all the 90s kids) style track.

When your doctor requests a full blood count, it's broken down into 13 parameters, looking at red cells, white cells and platelets. Each parameter and the relationship between the values can teach us a lot about what’s happening in your body, from inflammation to iron/B12/folate deficiency.

🔍 What We Learn From an FBC in IBD

Anaemia (low red blood cells or haemoglobin):
Common in IBD due to chronic inflammation, blood loss, or nutrient malabsorption (like iron, B12, or folate).

• Low Hb, low MCV → iron deficiency.
• Low Hb, high MCV → B12/folate deficiency.

Inflammation:
Ongoing inflammation often drives up white blood cells (WBCs), especially neutrophils. A raised platelet count (thrombocytosis) is also a classic sign of active inflammation in IBD.

Infection:
Flares and infections can look similar symptomatically. However looking at the individual white cells (remember white cells can be broken into 5 types: Neutrophils, lymphocytes, monocytes, eosinophils, basophils) we can differentiate between infection and inflammation, or even allergic responses such as parasitic infections.

Medication monitoring:
Some IBD drugs (like azathioprine or mercaptopurine) can suppress bone marrow. Regular FBCs help ensure your white cell and platelet counts stay within safe ranges.

Recovery or remission:
When inflammation settles, white cells and platelets often fall back to normal, and red cells gradually recover — so trends over time can tell a reassuring story.

Sample type: Whole blood in an EDTA anticoagulant.

🔥 C-Reactive Protein (CRP)

When inflammation kicks off in the body, this is one of the first, most reliable biomarkers. While not specific to IBD (not used to diagnose) it’s valuable to measure treatment response and flare progression. Released as part of the first line (innate) immune response - ill spare you details of much of its function. Partly because it’s complicated, partly because it’s just boring!

We spin your sample down, this separates the blood cells, platelets and clotting factors from the bit we want for this test - the serum. The serum, a yellow liquid contains all the proteins, including CRP. We then use a ‘high-sensitivity immunotrimeric assay’. Which essentially means we add a reagent that binds to the CRP protein, then we shine a light through it. Depending on how much this light scatters will give us a CRP result. Clever huh!

🔍 What CRP Tells Us in IBD

Detects active inflammation:
CRP rises quickly (within 6–8 hours) when inflammation flares — whether in the gut or elsewhere. It’s often used alongside faecal calprotectin to confirm whether a flare is truly inflammatory or more functional (like IBS).

Tracks disease activity:
Falling CRP levels after treatment suggest inflammation is settling. Persistently high levels can indicate ongoing disease activity or infection.

Helps distinguish flare vs. infection:
While both can raise CRP, very high levels (e.g. >100 mg/L) tend to point toward infection or severe inflammation.

Monitors treatment response:
Gastro teams use CRP trends to check whether biologics, steroids, or immunosuppressants are doing their job.

📊 Typical Reference Ranges

Normal: 0 – 5 mg/L

Mild elevation: 5 – 30 mg/L → low-grade inflammation or mild flare

Moderate: 30 – 100 mg/L → active inflammation

High: > 100 mg/L → severe inflammation or infection

>300 mg/L and we are likely calling the on-call doctor to potentially wake you up and bring you into AE.

(Each lab may have slightly different cut-offs depending on methodology.)

Erythrocyte Sedimentation Rate (ESR)

Full disclaimer - my least favourite test. However, you have to have some level of respect for a test that has been used for over a 100 years!! ESR measures inflammation. The concept: When inflammation is present, certain proteins in the blood (especially fibrinogen) make red cells stick together and form stacks called rouleaux. (note: this doesn’t happen in the body!)

These heavier clumps sink faster — resulting in a higher ESR. So that is it, we let the sample sit for 30 mins, and measure how much the clumps sink in mm per hour.

There are some cases where an ESR is valuable (looking at you rheumatology) but in IBD - it's just too unspecific of a test to use with any real value - despite a doctors love for requesting it.

That being said, used alongside a CRP:

• CRP and ESR raised → strong evidence of active inflammation.
• CRP high, ESR normal → early inflammation or acute infection.
• ESR high, CRP normal → may reflect chronic or resolved inflammation.

Can be influenced by other factors (this is the problem really): ESR isn’t as specific as CRP — it can be raised by anaemia, pregnancy, or age, so it’s always interpreted in context.

🚄The Automated Track:

To process over 10,000 samples a day, it wouldn’t be possible without an automated track system running 24/7. We load samples onto the track, and this will deliver the sample automatically to the analyser it needs to go to for that particular test. Only the biggest labs in the country will use an expensive (in the tens of millions of pounds) system such as this!

We use the Siemens Impeco Flex Lab X track - in fact, we were the first in the UK to use this new track. I’ll just show you a bunch of pictures here, because, look at all the pretty lights.

I hope I’ve been able to shed some light on how the lab helps with IBD. There are lots more valuable tests to mention that help us monitor your overall health, for example, how your liver function is dealing with treatment. I will likely add the ‘bigger picture tests’ to this article at some point.

We are often the forgotten people in the dark, dingy basement of the hospital - but the truth is we really do care about you. It’s our job to make sure the results the doctors receive are accurate and we do that with extreme pride (and a level of joy most people won’t understand).

So don’t forget about us, and we promise the next decade will be filled with improved diagnostic tests that will allow the best outcomes, early diagnosis and health of patients.

Any questions?

Chris;

Senior Biomedical Scientist in Haematology and Transfusion