Short Report: Care Delivery
Could FreeStyle Libre™ sensor glucose data support
decisions for safe driving?
 
Rayman1, J. Kr€oger2 and J. Bolinder3
1Ipswich Hospital NHS Trust, Ipswich, UK, 2Zentrum fur Diabetologie Hamburg Bergedorf, Hamburg, Germany and 3Karolinska Institutet, Stockholm, Sweden
Accepted 19 September 2017
 
Abstract
Aim Many countries require individuals with diabetes to adhere to standards regarding blood glucose testing in order to be granted or retain a driving licence. Currently, interstitial glucose results may not be used. The aim of this study was to determine whether interstitial glucose measurements using flash glucose-sensing technology can provide additional information to augment safe driving.
 
Methods Sensor data from two European studies (NCT02232698 and NCT02082184) of the FreeStyle Libre Glucose Monitoring System™ in insulin-treated Type 1 and Type 2 diabetes, 241 and 224 participants respectively, were used to determine the frequency of a low interstitial sensor glucose result (< 3.9 mmol/l) up to 4 h subsequent to a daytime (07:00–21:00 h) capillary blood glucose result ≥ 5 mmol/l.
 
Results
Within 4 h of a capillary blood glucose result ≥ 5 mmol/l a sensor glucose result of < 3.9 mmol/l occurred on
22.0% of occasions (2573 of 11 706 blood glucose readings) for those with Type 1 diabetes, and 8.4% of occasions
(699/8352) for those with Type 2 diabetes; 13.8% (1610/11 628) and 4.4% (365/8203) within 2 h, and 10.0% (1160/ 11 601) and 3.1% (254/8152) within 1.5 h. Analysis of sensor glucose results 5–7 mmol/l demonstrated the glucose trend arrow descending on 14.7% (1163/7894, Type 1 diabetes) and 9.4% (305/3233, Type 2 diabetes) of occasions.
 
Conclusions
Sensor-based glucose information with directional arrows has the potential to support assessment of safe glucose levels associated with driving and offers distinct advantages over blood glucose testing for individuals with Type 1 and Type 2 diabetes to concord with driving safety standards.
Diabet. Med. 000, 000–000 (2017)
 
Introduction
In the UK, the Driver and Vehicle Licensing Agency (DVLA) issues driving licences to comply with both European Union and UK legislation. Drivers with diabetes are subject to restrictions on their licences and for many individuals with diabetes there are additional standards to be met in order to obtain or retain their licence including: demonstrating safe glucose management, awareness of hypoglycaemia, no more than one severe hypoglycaemic event per year, and blood glucose testing relevant to driving [1].
 
The relatively recent European legislative requirement to report severe hypoglycaemia has prompted much discussion [2–4], whereas the obligation to test glucose levels prior to/during driving, which has been present in some countries for more than a decade, has received scant attention [5,6]. Diabetes specialists generally recommend glucose levels of ≥ 5 mmol/l as a ‘safe’ glucose threshold for driving [7]. Blood glucose testing is both a legal requirement [1] and considered crucial for safe driving with diabetes [8], particularly inthose treated with insulin [4]. UKdriverswithinsulin-treateddiabetesshouldtesttheirblood glucoselevelwithin2 hofthestartoftheirjourneyandatleast every 2 h into their journey [1].
 
Thus, according to this regulation up to 4 h could elapse after blood glucose testing before another test is required to continue driving.
 
Our aim was to evaluate data from participants performing capillary blood glucose testing and sensor-based flash glucose monitor-ing to determine the likelihood of hypoglycaemia occurring within this time period and whether interstitial sensor glucose resultscouldprovideadditionalinformationtoinformdriving decisions.
 
What’s new? Pearls
• This study shows new information on the potential risk of developing hypoglycaemia while driving at a ‘safe’ glucose level despite complying with blood glucose testing requirements associated with driving.
 
 
• Analysis of masked daytime flash sensor-based glucose data and capillary blood glucose results for individuals with insulin-treated Type 1 or Type 2 diabetes suggests that there is a significant risk of hypoglycaemia within the 4 h driving ‘window’ of blood glucose testing 2 h before/after starting to drive.
 
 
• Risk may be higher for individuals with Type 1 diabetes than those with Type 2 diabetes treated with multiple daily injection therapy.
 
Methods
The FreeStyle Libre™ Glucose Monitoring System is described in detail elsewhere [9]. Briefly, after sensor scanning, the reader displays 8 h of historic glucose data and current sensor glucose result with a glucose trend arrow indicating the direction and rate of change.
 
Arrows are defined as: ↑, increasing > 0.1 mmol/l/min; ↗ , increasing 0.06–0.1 mmol/l/min; ?, changing < 0.06 mmol/ l/min; ↘ , decreasing 0.06–0.1 mmol/l/min; and ↓, decreas-ing > 0.1 mmol/l/min.
 
We retrospectively analysed blood glucose results and interstitial sensor readings from two European randomized controlled trials (NCT02232698 and NCT02082184) to determine the frequency with which a low sensor glucose result (< 3.9 mmol/l) occurred after a capillary blood glucose result ≥ 5 mmol/l, the level considered safe for driving. In both studies the analysis was confined to waking hours (07:00–21:00 h) for a 14-day masked sensor wear (sensor glucose resultswerenotvisibletoparticipants). Studyone was in 241 adults with well-controlled Type 1 diabetes (HbA1c < 58 mmol/mol; < 7.5%) [10] and study two in 224 adults with Type 2 diabetes treated with intensive insulin therapy (HbA1c 58–108 mmol/mol; 7.5–12%) [11].
 
Analysis of 15-min historic interstiti glucose sensor results was performed for the 4-h period subsequent to a capillary blood glucose resultsof≥ 5 mmol/l.The frequencyofeach ofthedownward direction arrows was calculated for all current interstitial glucose sensor results obtained in 07:00–21:00 h between 5 and 7 mmol/l.
 
The frequency with which a low sensor glucose result (< 3.9 mmol/l) occurred after a sensor glucose result
5-7 mmol/l, separately for downward or upward trend arrows, was calculated. For individuals with Type 1 diabetes responses to the hypoglycaemia status questionnaire were compared to the control group using the Wilcoxon Rank Sum Test.
 
Results
The analysis showed that subsequent to a finger stick blood glucose result ≥ 5 mmol/l, a sensor glucose result < 3.9 mmol/l occurred within 1.5 h on 10.0% of occasions for adults with Type 1 diabetes (1160 of 11 601 blood glucose readings ≥ 5 mmol/l) and 3.1% of occasions for adults with Type 2 diabetes (254 of 8152), increasing to 13.8% (1610 of 11628) and 4.4% (365 of 8203), respec-tively, after 2 hours and to 22% (2573 of 11 706) and 8.4% (699 of 8352), respectively, after 4 h. A sensor glucose result of < 3.0 mmol/l occurred on 3.1%, 5.0% and 9.2% of occasions within 1.5, 2 and 4 h respectively for Type 1 diabetes, and on 1.0%, 1.5% and 3.1% of occasions for Type 2 diabetes.
 
Analysis of the same masked sensor wear period of sensor results between 5 and 7 mmol/l showed the trend arrow descending (↘ decreasing 0.06–0.1 mmol/l/min or ↓ decreasing > 0.1 mmol/l/min) on 14.7% of occasions for participants with Type 1 diabetes (1163 of 7894 sensor glucose readings) and 9.4% of occasions for those with Type 2 diabetes (305 of 3233). Analysis of a higher glucose range (8–12 mmol/l) showed the trend arrow descending on 13.4% and 9.6% of occasions, respectively. Further analysis of sensor glucose results 5–7 mmol/l showed that, for individuals with Type 1 diabetes, a sensor glucose level < 3.9 mmol/l occurred within 2 h on 38.8% of occasions with a downward glucose trend arrow and on 10.3% of occasions with an upward arrow, demonstrating the predic-tive value of the trend arrow.
 
Prior to randomization, participants in study one (in Type 1 diabetes) completed a hypoglycaemia status ques-tionnaire which included asking: ‘Do you check your blood glucose before driving?’ The optional answers were: yes always, yes sometimes, or no. By the end of the study, the likelihood of sensor glucose being checked before driving was significantly increased for intervention participants using FreeStyle Libre compared with controls using blood glucose testing (P = 0.0262) [10].
 
Discussion
Driving performance and safety are undoubtedly affected by hypoglycaemia, which is recognized as a cause for road traffic accidents [4].
 
Modern glucose monitoring technology is a significant component of diabetes care; to date, the DVLA does not recognize the use of interstitial glucose measurements when assessing ability to drive with diabetes.
 
An isolated blood glucose result > 5 mmol/l is perceived as an acceptable level for driving and, theoretically, following the ‘5 to drive’ principle and DVLA guidance, there could be 4 h between the blood glucose test performed prior to a journey and a blood glucose test taken after 2 h spent driving.
 
Our analysis of masked daytime sensor data for distinct advantages over isolated blood glucose tests.
 
This comprehensive glucose information could be invaluable to support decisions regarding safe glucose levels and ability to drive, hypoglycaemic risk assessment prior to driving to reduce the likelihood of an event whilst driving, and when to re-test on longer journeys.
 
Finally, although we did not set out to directly assess the impact of unmasked Freestyle Libre use on hypoglycaemia during driving, given that daytime hypoglycaemia was reduced in both Type 1 and Type 2 diabetes study groups in the two European randomized controlled trials described, it would be reasonable to expect that this would also be associated with a reduced frequency of hypoglycaemia during driving.
 
Sources
This retrospective study used data from two randomized controlled trials (NCT02232698 and NCT02082184). For both studies, Abbott Diabetes Care, in collaboration with the principal investigator for each country, designed the study protocol and provided all materials for the study. Abbott Diabetes Care was involved in the process for data collection, result reporting and funded medical writing services for these studies. For this submission, Abbott Diabetes Care was involved in the process for data collection and result reporting. Abbott Diabetes Care was not involved in the authors’ interpretation of the findings. The corresponding author had full access to the all the data in the study and, together with the authors, had final responsibility for the decision to submit for publication.
 
Acknowledgements
We thank all the individuals who contributed to the origi-nal data collection at the sites for both studies. We also thank Zo€e Welsh (Abbott Diabetes Care) for statistical support).
 
References
1 Driver and Vehicle Licensing Agency (DVLA). Assessing fitness to drive – a guide for medical professionals 2017. Available at https:// www.gov.uk/government/uploads/system/uploads/attachment_da ta/file/596959/assessing-fitness-to-drive-a-guide-for-medical-profe ssionals.pdf Last accessed 5 April 2017.
2 Min T, Dixon AN. Driving and insulin-treated diabetes. J Diabetes Nurs 2015; 19: 255–259.
3 Pedersen-Bjergaard U, Faerch L, Allingbjerg ML, Agesen R, Thorsteinsson B. The influence of New European Union driver’s license legislation on reporting of severe hypoglycaemia by patients with Type 1 diabetes. Diabetes Care 2015; 38: 29–33.
4 Graveling AJ, Frier BM. Driving and diabetes: problems, licensing restrictions and recommendations for safe driving. Clin Diabetes Endocrinol 2015; 1–8. Available at https://clindiabetesendo. biomedcentral.com/articles/10.1186/s40842-015-0007-3 Last acc-essed 23 June 2017.
5 Watson WA, Currie T, Lemon JS, Gold AE. Driving and insulin treated diabetes: who knows the rules and recommendations? Pract Diabetes 2007; 24: 201–206.
6 Graveling AJ, Warren RE, Frier BM. Hypoglycaemia and driving in people with insulin treated diabetes: adherence to recommendations for avoidance. Diabet Med 2004; 21: 1014–1019.
7 Gallen I, Amiel S, Robinson T. McKnight J, on behalf of the ABCD
Committee. Driving and hypoglycaemia: questions and answers. Pract Diabetes 2012; 29: 13–14.
8 Diabetes and Driving in Europe: A report of the second European working group on diabetes and driving, an advisory board to the Driving Licence Committee of the European Union, 2006 Available at http://ec.europa.eu/transport/road_safety/pdf/behavior/diabete s_and_driving_in_europe_final_1_en.pdf Last accessed 5 April 2017.
9 Bailey T, Bode BW, Christiansen MP, Klaff LJ, Alva S. The performance and usability of a factory-calibrated flash glucose monitoring system. Diabetes Technol Ther 2015; 17: 787–794.
10 Bolinder J, Antuna R, Geelhoed P, Kroeger J, Weitgasser R. Using novel flash glucose-sensing technology reduces hypoglycemia in individuals with Type 1 diabetes. Lancet 2016; 388: 2254–2263.
11 Haak T, Hanaire H, Ajjan RA, Hermanns N, Riveline J-P, Rayman G. Flash glucose-sensing technology as a replacement for blood glucose monitoring for the management of insulin-treated type 2 diabetes: a multicenter, open-label randomized controlled trial. Diabetes Ther 2017; 8: 55–73.
12 Cameron D, Harris FM, Evans JMM. Patterns of self-monitoring of blood glucose (SMBG) in insulin treated diabetes: analysis of a Scottish population over time. Diabetes Obes Metab 2016; 18: 729–731.
13 Inkster B, Pooley D, De Saxe H, Ahraf M, Frier B. Blood glucose testing by drivers with diabetes: a survey of glucose meter users. Br J Diabetes, Vasc Dis 2015; 15: 20–23.
14 Bell D, Huddart A, Krebs J. Driving and insulin treated diabetes: comparing practices in Scotland and New Zealand. Diabet Med 2010; 27: 1093–1095.
15 Jackson-Koku G, Morrison G, Morrison CL, Weston PJ. Insulin-treated diabetes and driving: what is the patient’s knowledge of current regulations? Br J Diabetes Vasc Dis 2010; 10: 31–34.
 
Artikeln i sin helhet i pdf inkl figur utan lösenord, special for you
 
Läs också gärna Röd Bok om hypoglykemi framtagen av Nationella Diabetes Teamet Sverige
Finns uppe till höger på www.dagensdiabetes.se såsom en klickbar pdf utan lösenord 10 sidor.
 
Ovan artikel i Diabetic Medicine visar, att bilkörning underlättas och blir säkrare med sensor-glukos-teknik.
 
Det är tekniskt närmast omöjligt för föraren att själv sticka sig i fingre och ta ett blodsocker under körning. Dessutom tar det nästan 120 sekunder, men scanning med Libre eller display på CGM möjliggör detta och tar bara knappt en sekund.
 
Sensor-teknik ger på enkelt och säkert sätt ett glukosvärde varje timme under bilkörning förutom innan bilkörning. Ett värde 5-6 mmol/liter eller högre eftersträvas innan eller under bilkörning. Extremt höga blodsocker kan också undvikas med sensorteknik.

Vid typ 1 och 2 diab m flerdos-insulin
 
Ovan artikel i Diabetic Medicine visar, att bilkörning underlättas och blir säkrare med sensor-glukos-teknik.

Det är tekniskt närmast omöjligt för föraren att själv sticka sig i fingre och ta ett blodsocker under körning. Dessutom tar det nästan 120 sekunder, men scanning med Libre eller display på CGM möjliggör detta och tar bara knappt en sekund.

Sensor-teknik ger på enkelt och säkert sätt ett glukosvärde varje timme under bilkörning förutom innan bilkörning. Ett värde 5-6 mmol/liter eller högre eftersträvas innan eller under bilkörning. Extremt höga blodsocker kan också undvikas med sensorteknik.

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