10 October 2018

In our third blog for NHS70, Dr Kate Earp goes back to the 1940s to explore how tests on blood and bodily fluids used to be conducted – before life-saving advancements in technology transformed our laboratories.

Chemical pathology, sometimes referred to as clinical biochemistry, is perhaps one of the lesser-known pathology specialties.  As a chemical pathologist, my job is to measure the amount of chemicals – minerals, drugs and proteins – within bodily fluids. Doctors and nurses rely on my interpretation of test results to diagnose, treat and monitor the health of their patients.

Chemical pathology now is a fundamental part of how we manage chronic illnesses like diabetes and osteoporosis, and many doctors like me spend much of our time in clinics seeing patients face-to-face. Looking back over developments in chemical pathology, though, it wasn’t always like this. At the birth of the NHS, testing was arduous and ineffective, its value largely misunderstood, until advancements in technology transformed our specialty into a cornerstone of modern medicine.


When the NHS was in its infancy in the 1940s, chemical pathology laboratories were very basic. They were only able to test patient samples for a small number of substances and only a minority of patients would have access to blood tests. It could take days to perform some of the tests and they were very labour intensive, with multiple steps to create mixtures of chemicals and then add the patient’s sample. And after all that work, the results produced were not even particularly accurate; only a rough estimate of the amount of a substance in a patient’s blood could be given.

For all these reasons, the laboratory was initially not seen as being that useful to patient care, often tucked away in the basement of the hospital, consisting of one small room with only a handful of staff. However, during the 1950s, new techniques were developed which enabled a greater number of substances to be measured and more helpful results produced.

One of the major advances came when ‘automated’ analysers were introduced; robotic machines would perform many of the tasks which were previously done by hand. With the introduction of computer processing, microchips were built into laboratory machines and connected to computers, allowing staff to interact with them more efficiently.

This raft of new, pioneering technologies enabled a greater number of samples to be processed in a shorter time frame. In particular, doctors were beginning to realise the usefulness of being able to test and monitor patients’ blood results, and performing blood tests started to become a routine part of patient assessment.


Today, chemical pathologists play a fundamental role in the health service, providing their expertise to other doctors and healthcare staff over the phone and at Multi-Disciplinary Team (MDT) meetings.  Many of our laboratories look very high-tech: purpose-built, large, modern buildings which house many complex pieces of equipment and at which hundreds of staff work.

Take my lab for example – we’re part of a large teaching hospital and process around 5,000 samples a day, from a combination of GP surgeries, hospital wards and outpatient clinics. From one tube of blood (which is about one teaspoon), over 20 different substances can be tested for, helping your doctor to monitor how your vital organs – such as the kidneys, liver and heart – are functioning. Blood test results are also able to help to diagnose conditions such as diabetes, heart attacks and certain kinds of cancer, with an accuracy which would have been unthinkable all those years ago. Abnormal results are automatically flagged and passed to a chemical pathologist like myself, so we can arrange for extra tests and advise GPs and other doctors on what to do next.

Now, much of the focus of the NHS laboratory is assisting with disease prevention. People who are at high risk of developing diabetes can be identified by a blood test and given clear advice on prevention. In addition NHS laboratories across the country now have an automated alert system that looks at blood tests from all patients whose kidney function is being monitored and detects if it has declined significantly. These alert means we can advise doctors on how take preventative action to stop the kidney from worsening further.


Technology is developing all the time and the accuracy with which we can measure changes in body chemistry makes personalising and monitoring treatment much easier.

New tests are emerging to help with the diagnosis of more and more conditions, with blood tests used to replace time-consuming tests that patients could find uncomfortable. For example, faecal calprotectin tests are used to rule out serious diseases of the gut – like Crohn’s disease or ulcerative colitis – where previously, patients would have to go to the hospital for a camera test or colonoscopy. Tests can also help us monitor how well the treatment is working; when I’m treating a patient for low bone density, a simple blood test will show the treatment’s impact around the three-month mark. Previously, we would have had to wait to see results in a bone density scan, which didn’t show any changes for a year or more.

Another emerging area is ‘personalised medicine’, since we now know that some patients respond better to certain treatments. Tests are now available which can predict how well a person will respond to medication – for example, before giving a patient a drug called azathioprine, used to treat conditions affecting the immune system, we can do a blood test that checks how well a patient will respond and if they are at risk of side effects. The doctor looking after the patient can then alter the dose of the drug accordingly.   

Of course, new developments and techniques are emerging every day. Chemical pathologists are always looking for ways of doing things better – indeed, when we’re overseeing laboratories, it’s a fundamental part of our job. Chemical pathology is a forward-looking speciality, which is what makes it so exciting to work in. Using cutting edge technology to improve patient care is what we do on a daily basis.