Is it feasible for European laboratories to use SI units in reporting results?

Introduction

Requesting and reporting clinical laboratory test results is an exercise in communication between multiple parties. It is also well known that successful communication between participants relies on a shared, comprehensible language [1]. All aspects of the laboratory service across the “total testing process” ultimately depend on concise, unambiguous and reliable communication: clinical terminology, nomenclature and measurement units in reporting results are the vehicle for correctly identifying an analyte or a panel of tests in a clinical request, for communicating the results to the clinician and/or including them in the electronic health record. However, despite the efforts made in recent years to produce a “harmonized” laboratory report both nationally and internationally, numerous critical aspects persist [2]. For this reason, in the present paper, written jointly by the EFLM Committee on Harmonization (C-H) and Committee Postanalytical Phase (C-POST), relevant insights are described that must be addressed in order to achieve a sustainable and widely adopted recommendation for harmonization in measurements units results.

Rationale for harmonization of measurement units in laboratory result reporting

In the current era of increased patient mobility and digitalization, efforts have been made to harmonize measurement units for laboratory result reporting, nationally and internationally, in order to meet the shared goal of providing patient-centered laboratory medicine [3]. The accessibility and exchange of healthcare data at a regional, national and international level can empower patients by providing access to their personal health data across the board and, as envisioned by the European Health Data Space (EHDS), can assist policy makers and researchers. Yet data sharing also incurs a considerable risk to patient safety in the event of a ‘mix-up’ of test names or units [4].

In the framework of laboratory procedures, professionals worldwide have recognized the need for completely comparable result reports, regardless of where and when a patient sample is processed [5], [6], [7], [8]. Comparability in result reporting is based on common measurement units. Initiatives and recommendations for the extensive adoption of the International System of Units (SI) since their introduction in the mid-twentieth century persist, rely on the efforts of international professional organizations: the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and International Union of Pure Applied Chemistry (IUPAC) which propose general rules for making appropriate measurement units accessible [9], [10], [11]. Moreover, ISO 15189:2022 calls for examination results to be reported “in SI units, units traceable to SI units, or other applicable units” (7.4.1.6 g), and for a comment to be included in the report when the use of different measurement units at a regional or national level may incur risk to the patient (7.4.1.7 d) [12]. Compliance with this requirement should be part of the assessment for laboratory accreditation.

Current situation in European countries

The adoption of harmonized SI units in European countries is the main goal of the EFLM Committee for Harmonization (EFLM C-H) [13]. In 2016, EFLM WG-H published the first survey on the use of the measurement units in European countries. The results showed that the road to harmonization of measurement units is arduous, since conventional units are deeply rooted in clinical practice and guidelines in some regions and countries. Resistance to the adoption of SI units depends, in particular, on clinicians’ concerns about the risk to patients incurred when results are reported in unfamiliar units. Afterwards a harmonization campaign was started with the proposal to basic changes be made, such as from mL to L as a volume unit, without the numeric result being changed, and that to modify the measurement units of plasma proteins from mg/dL or g/dL to mg/L and g/L, a 10 or 100-fold change in values being included [14]. In a survey conducted by EFLM C-H in 2023, progress, albeit slow, was noted in this process [15].

There are positive examples of the implementation of SI measurement units in specific countries and regions. In the United Kingdom, concerns were raised about the negative impact on diabetes patients caused by possible misinterpretation when HbA_1c units were changed from percentage to mmoles per mole. The strategy for their implementation included informing and educating healthcare personnel and patients. Data analysis of HbA_1c results from July 2009 to September 2011, one year before and after the adoption of mmol/mol, respectively, demonstrated the absence of negative outcomes in diabetes patients [16].

Penttilla I et al. described the approach for the implementation of SI units in HbA_1c reporting, and summarized the results of surveys sent to 41 societies from 2009 to 2014, and from External Quality Assessment (EQA) reports: the Authors underlined a positive trend in adopting SI units in European countries. Some professional societies, such as the Finnish Society of Clinical Chemistry (FSCC) and the Italian Society of Clinical Biochemistry (SIBioC), aimed to mitigate clinicians’ resistance to the adoption of SI units by recommending parallel reporting of the HbA_1c in mmol/mol and percentages. Subsequently, in 2016, FSCC and SIBioC recommended the exclusive use of SI units in HbA_1c reporting; this was readily adopted [17], 18].

In 2023, an EFLM WG-H survey attested that reporting of laboratory tests in SI units is supported by the government regulatory agencies or professional chambers in only some European countries, while in other countries national societies played an important role in the promotion of SI unit use [15]. Examples include the Czech Society of Clinical Biochemistry, the Croatian Society of Medical Biochemistry and Laboratory Medicine, the Italian Society of Clinical Biochemistry, and other national societies producing recommendations for good practice in various fields of laboratory diagnostics with analyte values in SI units [4], 19], 20]. In Belgium, for example, the government regulatory agency and laboratory medicine professionals implemented a pragmatic bottom-up approach to harmonize the units of clinical chemistry tests among Belgian clinical laboratories including conventional and SI units [21].

Harmonization does, however, represent a challenge in several countries, in which widespread reporting in conventional units persists.

Future of harmonization

Among medical specialties, laboratory medicine is the largest producer of structured data and precision medicine and personalized therapy require integration of laboratory and clinical data in clinical decision making [22]. Big data analysis and artificial intelligence applied to healthcare data can revolutionize the diagnosis and treatment of patients [23] The EFLM Working Group on Artificial Intelligence (WG-AI) suggested that data produced during sample processing should be categorized into peridata (i.e., data derived from the testing process that are relevant for the interpretation of the results within the clinical context), thus making the data actionable for patient care, and metadata (“data derived from the testing process that describe the characteristics and the requirements that are relevant for assessing the quality and the validity of laboratory test results”). A detailed description of the concept included measurement units as peridata, and data on intermediate calculations, including measurement units’ conversion, as metadata. The implementation of appropriate AI tools will enable flexibility and accelerate the widespread adoption of SI units in laboratory practice, obviating risk to patients due to misinterpretation [24].

The establishment of the European Health Data Space will open the possibility of the safe transfer of patients’ electronic health records between healthcare professionals in the EU countries. As electronic health records contain laboratory reports, intensive activities are required to create appropriate report format containing all elements needed for the corresponding interpretation [22]. It is essential that result reporting is harmonized before patient data are exchanged at the European level to avoid harm to patients.

Strategy for harmonization of measurement units should involve all stakeholders

The EFLM Committee on Harmonization (C-H) and Committee Postanalytical Phase (C-POST) propose a “general pragmatic approach” to improve harmonization of units of measurement for laboratory result reporting involving 4 key partners (Figure 1):

1. Institutional – government agencies, professional chambers, metrology institutes, national societies and international organizations of laboratory community and clinicians;

2. EQA (External Quality Assessment) providers;

3. Manufacturers of equipment, reagents, control materials, and information technology solutions;

4. Journal editorial and scientific boards.

Figure 1:

Key partners in the process of harmonization with different roles and responsibilities.

Special considerations

Tables 1–3 report on routine biochemical measurands, specific proteins and some endocrinology parameters with appropriate measurement units.

However, some concerns regarding reporting in SI units results for specific measurands arise:

1. Reporting of enzyme activity in U/L is widely accepted. Therefore, may be challenging to implement the SI enzyme activity unit, μkat/L. However, for several decades the SI unit has been widely used in laboratories in some countries such as the Czech Republic.

2. Use of SI reporting units for therapeutic drug monitoring. The choice of the measurement units in this field of laboratory testing depends on local regulations. A consensus of clinicians, pharmacists and laboratory medicine specialists on the selection of measurement units is needed for safe patient management and dosage adjustment decisions. It may be more practical to continue to report certain drug concentrations in conventional units of µg/L, mg/L or g/L rather than µmol/L or mmol/L in view of the fact that drug dosage calculations are typically performed in conventional units.

Conclusions

This opinion paper lays down the rationale of why harmonization of units in result reporting is important and proposes a “general pragmatic approach” to get closer to the goal. We identified the key stakeholders to involve in the harmonization process concerning measurement units in reporting results. The complexity of harmonization across the European countries, is a particular challenge and there is a high risk of failure to achieve the goal if all different stakeholders do not contribute to the mandate. According to the results from 2023 survey [15], there are also specific fields in laboratory medicine, such as coagulation testing, that actually require significant and hard harmonization processes in measurement units; however the topic of this paper was not to describe those in detail. A shared activity with specific working groups and national and international clinical societies are in progress to provide a final, shared recommendation.

In deciding how much harmonization is necessary, it must be borne in mind that the goals should be to remove known avoidable variations in current practices where the measurement units in reporting results represent a relevant focus. The foundation of the shared recommendations should serve for future requirements that not all are known yet. The development of AI is certainly among these “future unknown” Therefore, laboratory harmonization is hardly a destination but rather an ongoing journey of constant improvement, in which multi-stakeholders input is essential.