Time to rationalise our use of inflammatory markers

Injudicious use of inflammatory marker testing for non-specific symptoms is likely to cause more harm than good.
I can still remember my first weekend on call as a surgical house officer - rushing around on the morning post-take ward round when a radiology request card was thrust in my hand, and I was sent like a lamb to the slaughter to the on-call radiologist to request an ultrasound for a patient with suspected cholecystitis.

This particular radiologist was well known to have a penchant for making new house officers crumple if we dared request out of hours radiology without the most water-tight argument. ‘HOW WOULD THIS INVESTIGATION CHANGE YOUR MANAGEMENT?’ came the well-rehearsed mantra. Well, frankly I had no idea; I’d only been a doctor for a week and had no clue if the surgeons were planning to operate over the weekend or not, so I was duly sent packing back to my senior to get more information.

Brutal though that first encounter was, it did teach me an important lesson - knowing what test to use, when and for what conditions is a crucial skill in medicine, particularly in General Practice. A really excellent study in the July BJGP brought into sharp focus an area where there is wide variation in practice, namely the use of inflammatory markers for diagnosis.

Inflammatory marker testing in primary care is rising every year, but little is known about whether this is helping diagnostic accuracy or simply generating a cycle of further testing for little gain. Increasingly it appears we are doing CRP and ESR to try to rule out serious disease and reassure us and our patients, but is this helping? Well, this was one of the questions posed by an excellent cohort study in the July 2019 BJGP. The authors looked at a large cohort from the CPRD from 2014, including just under 160,000 patients that had inflammatory marker testing (ESR, CRP or plasma viscosity) and just under 40,000 matched controls who did not have testing. Those with known cancer, auto-immune disease or chronic infection were excluded and the authors then reviewed the numbers of participants who developed serious disease (including cancer, auto-immune disease and infections) in those with raised or normal inflammatory markers. Much of the testing was for non-specific symptoms (with tiredness being one of the commonest reasons for testing) and the results showed that of the ~28% who had raised inflammatory markers, 85% of these had no significant disease (i.e. 85% were false positives). 

The study went on to confirm that these false positives led to huge numbers of unnecessary further tests, appointments and referrals. The authors estimated that for every 100 inflammatory marker tests done, it would generate ~24 false positives which would lead to 71 further GP appointments, 23 further blood tests and 2-3 referrals, all for very little benefit.

The other issue the study confirmed is that inflammatory marker testing showed very poor sensitivity for serious disease, meaning they are generally not suitable as rule-out tests either. I was particularly interested in those with a cancer diagnosis - based on the results 21/1000 tested had cancer with 10 having positive inflammatory markers and 11 negative results i.e. doing a CRP/ESR added no value to diagnosis of cancer, and in those with negative results there is a real risk of delayed diagnosis by giving us and our patient false reassurance. The one exception to this would be suspected Myeloma - previous research in the BJGP in 2018 showed that a combination of a normal Hb, ESR and calcium was sufficient to rule out myeloma in the vast majority of the cases, but this is clearly the exception not the rule with inflammatory marker testing.

The message from this research seems quite clear - injudicious use of inflammatory marker testing for non-specific symptoms is likely to cause more harm than good. It will generate huge numbers of false positives, and subsequent unnecessary onward testing and appointments, as well as false reassurance in some patients with normal CRP/ESR who do have serious underlying disease, and a risk of delayed diagnosis. ‘HOW WOULD THIS INVESTIGATION CHANGE YOUR MANAGEMENT?’ - a question we should all be asking when considering use of inflammatory marker testing in primary care.

This article was originally publish on the NB Medical Education Hot Topics Blog on 1 August 2019.

{{commentCount}} comment(s). You must be logged in and AHPRA verified to view and comment. Login here.

Dr Robert Walker

Rob Walker is a GP in Basingstoke. He is a member of the NB Medical team charged with reviewing and writing material for the Hot Topics course and book.

The latest healthcare news from medcast

Telehealth: How does it work In Practice
Telehealth: How does it work In Practice

We are all starting to do telehealth in the current climate to protect us, our staff and our patients. Many of us feel slightly out of our depth. Here are some quick tips to help you in your practice.

Telehealth and COVID-19 Update
Telehealth and COVID-19 Update

As the number of cases of COVID-19 increases exponentially in Australia many of us will be exploring the new telehealth item numbers. The information on these seem to be changing daily, but currently these are the key things to know.

Coronavirus
Coronavirus

Since the start of 2020, coronavirus has hit the world and caused unprecedented levels of concern among public and health professionals alike.

Oropharyngeal Airways in Paediatric Patients
Oropharyngeal Airways in Paediatric Patients

Oropharyngeal airways (OPAs) have some additional considerations when utilising in paediatric patients, to ensure safe use in children.

Why are we so bad at making the self-care message stick?
Why are we so bad at making the self-care message stick?

“I looked at that list you gave me.” There was no mistaking the anger in my patient’s eyes. “I can’t believe you would suggest that I could get better from this by taking some deep breaths or going for a walk! I don’t think you understand my situa...

PODCAST: Iliotibial Band Syndrome
PODCAST: Iliotibial Band Syndrome

Milo, aged 26, comes to see you with lateral knee pain. As GPs how do we diagnose, treat and manage this?

Easing the Lingering Symptoms of Depression
Easing the Lingering Symptoms of Depression

Despite our best efforts, most patients who experience depression are left with residual symptoms that linger beyond the completion of treatment. Whether it be low motivation, low mood, self-criticism, guilt or worry, residual symptoms of depressi...

Recognising and responding to deteriorating patients: a matter of life or death
Recognising and responding to deteriorating patients: a matter of life or death

The most recent update of the Australian Institute of Health and Welfare’s (AIHW) Deaths in Australia report shows that in 2017 there were a total of 160,909 recorded deaths in Australia. 50% of these were found to be potentially avoidable within ...

A new approach to mental health care
A new approach to mental health care

I’m a GP with a special interest in mental health. For the past three years I have been working with Medibank health solutions to support the implementation of a range of programs for people with chronic and complex health conditions.

Out of Office - Dr Simon Curtis
Out of Office - Dr Simon Curtis

Find out more about Simon, co-founder of the Hot Topics course internationally in his 'Out of Office' before seeing him in person at Hot Topics Australia.

Team GP – why we need to learn together
Team GP – why we need to learn together

Learning is all about making some sort of change. As GPs, it can be easy for us to think of our learning simply as a process we go through to tick a box. But maybe we should be thinking more deeply about the types of learning that truly cause us t...

PODCAST: Hypocalcaemia
PODCAST: Hypocalcaemia

Sundeep, a 63 year old office worker, presents with intermittent nagging loin pain and achy muscles.

Stop Before You Block: A Block Time-Out
Stop Before You Block: A Block Time-Out

The Stop Before You Block (SB4YB) initiative is a patient safety campaign designed to help reduce the risk of inadvertent wrong-sided anaesthetic blocks.

Moments of Joy
Moments of Joy

This year I’ve decided to practice what I preach. I’m starting with something that has evolved from last year’s eye-opening experience with keeping a gratitude diary when, along with other members of my team at work, I participated in the 6-week M...

Vaping - Friend or Foe?
Vaping - Friend or Foe?

Where are we with vaping? Are e-cigarettes the shining knight who will rid the world of cigarettes or dangerous products wrapped up in clever marketing with the 'unintended consequence' of luring young people into the world of smoking?

On being a GP seeking help
On being a GP seeking help

I had an interesting experience at my GP recently. I don’t go to the GP very often. Mostly I don’t get sick. Sometimes I treat my own ills or just soldier on. On the few occasions that I have been to see someone about something concerning me, my ...

Let’s talk about self-soothing
Let’s talk about self-soothing

I talk to a lot of health professionals and it amazes me how often people look at me blankly when I introduce the subject of self-soothing activities. As the conversation progresses I can see most of the blank looks turn to some degree of understa...

Can I have medical cannabis on PBS doctor?
Can I have medical cannabis on PBS doctor?

I’ve been asked this question twice in the last month. Once by a 70 year old patient who has taken up smoking weed to control her neuropathic pain, let’s call her ‘Rachel’. And the other a young man aged 26 (Sean) who is smoking cannabis to help c...

Standardising Emergency Numbers: The Push for 2222
Standardising Emergency Numbers: The Push for 2222

The move to standardise emergency numbers within hospitals, to make them similar to the standardised emergency numbers that are utilised in the community setting, is gaining momentum.

PODCAST: Acute Diverticulitis
PODCAST: Acute Diverticulitis

Stan, aged 80, comes to see you with left side abdominal pain and a low-grade fever. This is a classic example of a common problem doctors face in General Practice. In our Podcast we discuss Diagnosis, Assessment, Management & Referral.

Join Medcast. It's free and you'll get instant access to essential healthcare news, research and more.

Already a member? Sign-in