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Preanalytical challenges and their clinical impact in point-of-care testing
The European Society for Emergency Medicine (EUSEM) held their annual congress on October 27th to 31st, 2021 in the Portuguese city of Lisbon, to promote education, training and research in European acute care. The event’s hybrid format allowed for more than 2000 in-person and virtual delegates from over 70 countries.
On October 30th, BD Life Sciences, Integrated Diagnostic Solutions (IDS), hosted a lunch-time educational workshop entitled, ‘The impact of non-reported point-of-care testing (POCT) errors on patient care and hospital resources.’
The event was moderated by Anthony Malpass, Clinical Project Manager, BD IDS and presented by a team of expert guest speakers:
- Professor Kevin Rooney, Consultant Anaesthetist and Intensivist, United Kingdom
- Dr Antonio Buño Soto, Point of Care Director and Head of Laboratory Medicine, Spain
- Dr Ulf Martin Schilling, Consultant in Emergency and Internal Medicine, Sweden
Throughout the presentation, attendees were interactively polled for their clinical opinions on a number of patient case studies to demonstrate the impact of POCT errors and their clinical consequences, even among experienced professionals.
POCT and the imperative of test quality
Professor Rooney explained that in a busy emergency department (ED), “POCT can reduce turnaround time ‘from vein to brain’ by bringing diagnostic testing to the patient’s bedside”.
The ideal POCT kit meets the standards established by the Institute of Medicine’s Six Domains of Health Care Quality: it is safe, efficient, and effective to use, and generates timely results which assist in providing equitable and person-centred care.1
So, POCT in the ED has the potential to2:
- Decrease delays to treatment
- Increase ED efficiency
- Positively influence patient care
- Negate the effects of overcrowding
The key word in that statement is ‘potential.’ For to meet this potential, the testing has to be of high quality. And therein lies the problem – the reliability of POCT results.
“POCT does not mean ‘platinum-plated’” –Dr Antonio Buño Soto
Clearly if the sample is compromised, so too is the result.3 In a Stat laboratory setting, up to 61.9% of errors occur at the preanalytical phase due to the manual nature of sample collection.3,4 Similarly, POCT is susceptible to preanalytical error from poor sample quality and improper handling.5
Anyone, even an experienced clinician working in a busy ED, may miss a potentially erroneous POCT result, one that causes the development of a faulty clinical management plan. To prove the point, our audience was polled on the real-life clinical cases outlined below.
Case Study 1: 30 weeks pregnant: emergency caesarean section or not?
For this first case, think:
“Would an incorrect POCT haemoglobin (Hb) force you down an incorrect management plan?” –Professor Kevin Rooney
A pregnant patient presented to the ED with 72-hour back pain radiating to the front, along with dizziness, shortness of breath, malaise and reduced foetal movement. She experienced increased urinary frequency from 20 weeks gestation. She also has a childhood history of vesico-ureteric reflux.
On examination, the patient looked unwell: diaphoretic, anxious and writhing around the bed.
- Glasgow Coma Scale (GCS) 14 with Verbal 4 (confused)
- Temperature 37.5°C
- Heart rate 138 BPM, blood pressure 82/63, capillary refill time 3 seconds
- Respiratory rate 30, oxygen saturation 92% on air, reduced air entry at bases
- Bloody show on her sanitary towel
A POCT arterial blood gas analysis showed a partially compensated metabolic acidosis, with a carbon dioxide partial pressure of 3kPA, a lactate of 2.6 mmol/l and an Hb of 80 g/l.
Was the patient experiencing a concealed antepartum haemorrhage, requiring emergency caesarean section? 33% of the audience thought so.
One hour later, the patient’s formal laboratory results arrived: white blood count 2.3 x109/l, Hb 106g/l, Haematocrit 0.3 l/l, C-reactive protein 100 mg/l. A diagnosis of urosepsis/pyelonephritis was confirmed.
Consider this: would the low Hb results guide you down an erroneous patient management plan? They did for one third of the audience.
Urea and Electrolytes (U and E) and hidden haemolysis
To further illustrate the impact of preanalytical errors, Dr Ulf Martin Schilling outlined the cases of three young women, each who presented with very similar complaints: severe abdominal pain and general malaise over the previous 24 hours, with vomiting, diarrhoea, nausea and vertigo. Their clinical observations were also similar and generally unconcerning.
Then the Urea and Electrolyte results arrived:
| Result | Case Study 2 | Case Study 3 | Case Study 4 |
Potassium (K+) mmol/l | 3.2 | 4.2 | 5.2 |
| Sodium (Na+) mmol/l | 128 | 135 | 122 |
| Creatinine mmol/l | 65 | 95 | 110 |
| Chloride (Cl-) mmol/l | 90 | 98 | 90 |
Clinical interpretation | Spurious result | Hyperchloraemic hypokalaemic alkalosis + pseudohyperkalaemia | Addisonian crisis |
How can it be that while the women presented similarly, according to the blood results, one had a simple gastroenteritis while the other was undergoing a potentially life-threatening Addisonian crisis?
Haemolysed samples can give an abnormally high K+ level or mask a true hypokalaemia. In central laboratory processes, haemolysis is flagged for a visual inspection of the centrifuged sample and subsequent analysis of the Haemolysis Index. However, with POCT these tools are not available, meaning haemolysed samples are not identified.
The hidden cost of preanalytical errors
Following the case presentations, Dr Antonio Buño Soto presented the causes and costs of these preanalytical errors. He demonstrated that most errors in laboratory medicine occur in the preanalytical stage during patient preparation, blood collection and sample handling/transport.
He noted that the impact of erroneous results can reach from patient management and safety to even the institute economy.
But what about the impact of POCT preanalytical errors within the ED? According to Dr Schilling, “Emergency departments have quite a high level of pre-analytical error”. As illustrated by our clinical cases, POCT errors in the ED can produce misleading readouts, with similar implications for patient care and resource use.
What is the solution?
Dr Schilling advised the audience to “be sure that whatever is done, is of high quality”. The aim is to produce POCT results that are equivalent to those generated by a central laboratory.
But what does this mean in practice? A multidisciplinary approach involving laboratory professionals is the best way to mitigate POCT errors and to improve patient care. The central laboratory should lead and control every aspect of POCT: from the outpatient clinic to the hospital ward, from the intensive care unit to the physician’s office.
Multidisciplinary involvement is supported by professional healthcare organisations. ISO22870:2016, which is intended to be used in conjunction with ISO15189, gives specific requirements applicable to point-of-care testing, such as the creation of a POCT network and committee, whose members include representation from the central laboratory and who oversee all aspects of POCT management.6
When interpreting POCT results, stop and think
POCT is vulnerable to similar preanalytical errors as central laboratory testing but lacks the mitigating technology inherent to those systems. Even if the POCT is impeccably managed and operated, clinical discretion is required when actioning results. As Anthony Malpass said, “An analyser even if well maintained, well quality checked, well controlled and well managed, is still capable of giving you a wrong result. It is based on the sample put into it. If the sample is no longer representative of the patient, you are making judgements which could have significant consequences.”
Every caregiver’s primary aim is to provide the best possible care to all patients. Every clinical sample represents a human life, a person whose wellbeing relies on the accuracy of that sample. A good clinical decision is only supported by sound clinical results, and sound results can only come from a quality sample. If we depend on POCT to inform our clinical management, we must ensure that the sample remains representative of the patient’s true clinical picture.
Though complex and multi-faceted, mitigating preanalytical errors in POCT can be supported by the integration of a dedicated, diverse POCT team that gives the ED central laboratory support. Training, device maintenance and safety measures can then be rolled out, with evidence-based practice at the forefront.
However, even if your ED has an exemplar POCT system in place, Professor Kevin Rooney cautioned the audience, “If you get a POCT result think, is that blood result consistent with the patient?”
References:
1 Agency for Healthcare Research and Quality https://www.ahrq.gov/talkingquality/measures/six-domains.html [Accessed 29/04/2022]
2 Rooney K and Schilling M. Point-of-care testing in the overcrowded emergency department--can it make a difference? Critical Care 2014 18:692 DOI: 10.1186/s13054-014-0692-9
3 Wallin O, et al. Patient-centred care--preanalytical factors demand attention: a questionnaire study of venous blood sampling and specimen handling. Scand J Clin Lab Invest. 2007;67(8):836-847. doi: 10.1080/00365510701370675
4 Carraro P, Plebani M. Errors in a stat laboratory: types and frequencies 10 years later. Clin Chem. 2007;53(7):1338-1342. doi: 10.1373/clinchem.2007.088344
5 Kazmierczak SC, Morosyuk S, Rajkumar R. Evaluation of Preanalytical Point-of-Care Testing Errors and Their Impact on Productivity in the Emergency Department in the United States. J Appl Lab Med. 2022 Jan 7: jfab158. doi: 10.1093/jalm/jfab158
6 POCT Accreditation ISO 15189 and ISO 22870: Making the Point. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8343036/ [Accessed 29/4/2022]
13.06.2022
