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Review

Self-monitoring of blood glucose in noninsulin-treated type 2 diabetes: an overview

, , , , , & show all
Pages 155-163 | Published online: 27 Sep 2022

Abstract

Introduction

The effectiveness of self-monitoring of blood glucose (SMBG) in noninsulin-treated patients with type 2 diabetes (T2DM) remains unclear. We aimed to review the trials investigating the effects of SMBG in this population.

Methods

Medline was searched until June 29, 2009. Randomized controlled trials (RCTs) of at least 12 weeks’ duration were included. Data on the following aspects were gathered: patient and study characteristics, effects on HbA1c, quality of life and treatment satisfaction, and methodological quality.

Results

The search revealed 9 original RCTs. These studies were very heterogeneous, and 5 were classified as of high quality. The studies with the best methodology did not show an effect of SMBG on HbA1c, the studies with the worst methodological quality did. Two out of the 4 studies that assessed quality of life showed a significant change in favor of the control group, 1 study showed a significant change in favor of SMBG.

Discussion and conclusion

We found an inverse relation between study quality and efficacy of SMBG. At this moment, there is no basis for general use of SMBG in noninsulin-treated T2DM patients.

Introduction

Self-monitoring of blood glucose (SMBG) is an important tool in the management of diabetes mellitus. Patients with type 1 diabetes frequently measure their blood glucose to evaluate and, if necessary, to adjust insulin treatment and lifestyle, and to detect hypoglycemia. It is recommended that patients should measure their blood glucose at least 3 times daily.Citation1 Although effectiveness of SMBG has been established for insulin-treated patients with type 2 diabetes (T2DM), the optimal frequency and timing of SMBG have not yet been established.Citation2,Citation3 There is still much debate about the use and effectiveness of SMBG in noninsulin-treated T2DM.Citation4 Many trials have investigated the effects of SMBG in this specific group and many (systematic) reviews have been written on this topic with conflicting conclusions.Citation5

In insulin-treated patients SMBG can lead to (instant) insulin dose adjustments, thereby improving glycemic control and/or reducing episodes of hypoglycemia. This cascade is not applicable for patients not using insulin, because an instantaneously modifiable factor is lacking. Still, there are theoretically advantages of SMBG in this population as well. For instance, data of SMBG could be used during periodical consultation with the diabetes health care provider to start or titrate blood glucose-lowering agents. Furthermore, based on the measured blood glucose, patients could adjust physical activity or food intake, or both.

Many aspects need to be considered when evaluating the effects of SMBG in noninsulin-treated patients. Firstly, how SMBG is used depends on the patient’s level of diabetes education. Without any knowledge of the patient about the values to strive for it will be merely self-measurement and health care providers are needed to interpret the results and give advice on how to adjust physical activity and diet. Whereas, when the patient is fully informed about the treatment goals and is educated about how to achieve these goals, SMBG could function as a tool for self-regulation. Secondly, the frequency of measurements varies; SMBG can be performed infrequently or each day at fixed times, pre- or postprandial, or both. Thirdly, the population of noninsulin treated T2DM patients is heterogenic and may use SMBG differently. For example, newly diagnosed patients, who just started a specific diet versus patients on a maximum dosage of oral blood glucose-lowering agents, when insulin therapy will have to be the next step. Or patients in good glycemic versus patients in persistent poor glycemic control. Fourthly, in some situations the primary goal of the patient and the health care provider could not be to improve glycemic control with SMBG, but to improve the patient knowledge of diabetes and the effects of different behavior on glucose levels and thereby influencing nonclinical factors such as well-being and treatment satisfaction. Furthermore, performing SMBG includes the patient drawing blood from his or her finger tip regularly. This procedure can be painful or frightening and may also have its impact on well-being on its own.

We aimed to review trials investigating the effects of SMBG in noninsulin-treated patients with T2DM. We did not focus only on the effects on glycemic control, but also on the effects on health-related quality of life and treatment satisfaction as well as on the methodological quality of the trials.

Methods

Inclusion criteria of studies

Randomized controlled trials (RCTs) of at least 12 weeks’ duration were included for this review. These studies should have included noninsulin-treated patients with T2DM, the intervention group should use SMBG, and the control group should use any other form of measurement of glycemic control or should continue to receive usual care. Trials should have included measurements of glycosylated hemoglobin (HbA1c).

Search strategy

Medline was searched until June 29, 2009 using PubMed with the following combination of free text words and MeSH-terms:

(((self-measur* OR self-monitor*) OR (“Blood Glucose Self-Monitoring”[Mesh])) AND ((“Diabetes Mellitus”[Mesh]) OR (diabete* OR diabeti* OR diabeto*)))) AND (((randomized controlled trial[Publication Type] OR (randomized[Title/Abstract] AND controlled[Title/Abstract] AND trial[Title/Abstract]))) OR systematic[sb].

Articles were selected for full text reading based on their title and abstract by two of the authors (NK and JH). The references of the systematic reviews were checked for additional studies as well.

Data selection

The selected RCTs were carefully read and data on the following topics were gathered systematically by two of the authors (NK and KJJH): patient characteristics, treatment modality, duration of intervention and control, type of intervention and control, and the number of patients in each treatment arm. Data on changes in HbA1c and quality of life and treatment satisfaction were extracted both within and between treatment groups. Methodological quality of the trials was assessed using the same method as Welschen et al used in their Cochrane review.Citation4 Eleven items pertaining to internal validity were applied:

  1. Was the method of randomization adequate?

  2. Was the treatment allocation concealed?

  3. Were the groups similar at baseline regarding the most important prognostic indicators?

  4. Was the patient blinded to the intervention?

  5. Was the care provider blinded to the intervention?

  6. Was the outcome assessor blinded to the intervention?

  7. Were co-interventions avoided or similar?

  8. Was the compliance acceptable in all groups?

  9. Was the withdrawal/drop-out rate described and acceptable?

  10. Was the timing of the outcome assessment in all groups similar?

  11. Did the analysis include an intention-to-treat analysis?

Each item had a rating scale of “yes”, “no” or “don’t know”. Studies fulfilling 6 or more of the 11 quality criteria were considered to be of “high quality”. All studies scoring less than 6 of the criteria were rated as “low quality”. Studies of low methodological quality were not excluded.

Results

Studies

The initial search identified 427 publications, of which 31 papers were selected for full text reading based on title and abstract. These 31 studies included 17 potential systematic reviews and 14 potential RCTs. From the RCT selection, 1 trial was excluded because of the inclusion of patients using insulin.Citation6 In 2 studies, the intervention as well as the control group used SMBG.Citation7,Citation8 For 1 study 2 referencesCitation9,Citation10 were found and for another study 3 references were found.Citation11Citation13 One additional RCTCitation14 was selected from the reference list of a systematic review.Citation15 Consequently, 9 original RCTs were selected and will be discussed.Citation9Citation14,Citation16Citation21 Both authors (NK and JH) obtained the same results for the literature search. Of the 17 potential systematic reviews, 14 references qualified.Citation4,Citation15,Citation22Citation33 Four references, however, were all based on the Cochrane review of Welschen et al.Citation4,Citation24,Citation27,Citation28 Two references were based on the review of Coster et al.Citation31,Citation32

Patient characteristics and treatment modality (see )

Table 1 Randomized controlled trails of self-monitoring of blood glucose (SMBG) in patients with type 2 diabetes not using insulin: patient characteristics

The included trials were almost all performed in Western Europe or the United States. One study included patients from several Eastern Europe countries and from Malaysia and Iran.Citation14 Except for the study of Farmer et alCitation11Citation13 all studies included patients in poor glycemic control indicated by HbA1c values ranging from 8.1% to 12.0% (mean values). The study by O’Kane et al included only patients with new onset diabetes.Citation21 The duration of diabetes in the other studies ranged from 2.8 to 12.7 years. The majority of the included patients was treated with oral blood glucose-lowering agents. Furthermore, most patients were obese, and did not use or infrequently used SMBG prior to the study.

Study characteristics (see )

Table 2 Randomized controlled trails of self-monitoring of blood glucose (SMBG) in patients with type 2 diabetes not using insulin: study characteristics

All studies had a duration of 24 weeks or longer, with the longest study duration being 12 months. Studies differed substantially regarding requested number of blood glucose values, ranging from 6 to 42 times a week, with most studies collecting some postprandial values. Patients in most studies received target glucose values to strive for. These targets were different between studies, and more recent studies used lower target values. Glucose values were mostly part of collected information which was used to give advice on lifestyle responses. In 4 studies strict algorithms were used to adjust blood glucose-lowering therapy.Citation14,Citation16,Citation17,Citation21 From the published data from the remaining 5 studies it is not clear whether and if so on what basis therapy was adjusted.Citation9Citation13,Citation18Citation20 A dietician participated in most studies or specific advices about diet were given (in 1 study education about counting carbohydrates was given). Patients in the less intensive SMBG group of the study by Farmer et al did not receive such advice.Citation11Citation13 In some studies much time and effort of a multidisciplinary team was invested to support the patient with SMBG, while in another study SMBG was given to the intervention group without support or education. In 2 studies, the control group performed urine testing of blood glucose.Citation16,Citation18 In other studies usual care was continued or HbA1c was measured periodically in the control group. In the studies by Allen, Davidson, Fontbonne, Guerci, and in the less intensive group in the study by Farmer, it appears that except performing SMBG or not, no differences exist between the intervention and control group.Citation11Citation13,Citation16Citation19 In other studies, the SMBG group received also additional information or got personal advice about diet and exercise.

Methodological quality of studies (see )

Table 3 Randomized controlled trails of self-monitoring of blood glucose (SMBG) in patients with type 2 diabetes not using insulin: methodological quality

Four studies were of low quality, 5 studies were of high quality. The studies published by Farmer, Davidson, and O’Kane are the studies with the best methodology. However, all these studies had problems with the compliance of patients performing SMBG.Citation11Citation13,Citation17,Citation21 In the study by Davidson et al compliance was less than 50%.Citation17 The study described by Farmer et al reached compliance rates of 67% and 52% in the less and more intensive intervention groups, respectively. In the study by O’Kane et al 34% of the patients performed less than 80% of the requested measurements.

Effect on glycemic control (see )

Table 4 Randomized controlled trails of SMBG in patients with type 2 diabetes not using insulin – study results: HbA1c

Three studies found a significant beneficial effect on HbA1c of SMBG compared to the control group.Citation9,Citation10,Citation19 In the study by Guerci et al HbA1c decreased from 9.0% to 8.1% after 6 months. This decrease in HbA1c was ~0.3% more compared to the decrease in found in the control group (P = 0.009). In the study by Schwedes et al HbA1c decreased from 8.5% to 7.5%, which was ~0.5% (95% CI −0.77, −0.11) more compared to the control group. In the study by Barnett et al HbA1c decreased from 8.12% to 6.95%, which was 0.24% (95% CI −0.45, −0.03) more compared to the control group.Citation14 Muchmore et al found a nonsignificant benefit of SMBG of ~0.7%.Citation20 In the other studies nonsignificant differences between SMBG and control groups were between −0.2% and 0.1%.

Effect on quality of life and treatment satisfaction (see )

Table 5 Randomized controlled trails of self-monitoring of blood glucose (SMBG) in patients with type 2 diabetes not using insulin – study results: Quality of life and treatment satisfaction

In 4 studies, quality of life and treatment satisfaction were assessed using questionnaires. In the study of Muchmore et al no differences in quality of life were found between the intervention (SMBG) and control group (usual care).Citation20 Although no significant difference was found for the total score on the patient well-being questionnaire in the study by Schwedes et al, 2 sub items (“depression” and “lack of well-being”) improved with SMBG compared to control.Citation9,Citation10 In contrast with these findings, 2 more recent trials reported that SMBG was associated with lower quality of life.Citation11Citation13,Citation21 In the study by Farmer et al quality of life, as measured with the EQ-5D questionnaire, was lower in the more intensive intervention group compared to the control group.Citation11Citation13 In the study by O’Kane et al the depression scale of the well-being questionnaire was significantly worse in the SMBG group compared to the control group.Citation21 No differences were found concerning treatment satisfaction.

Discussion and conclusion

Nine RCTs investigating the efficacy of SMBG in noninsulin-treated patients with T2DM have been published so far.Citation9Citation14,Citation16Citation21 One third of the studies reported a positive effect of SMBG on HbA1c ranging from a 0.2% to 0.5% decrease. None of the studies published found a negative effect of SMBG on HbA1c. The evidence is more conflicting about the effects on quality of life. SMBG, as discussed in the introduction, is a complex intervention, although one can debate whether or not SMBG should be classified as an intervention in patients who “only” self-monitor without any form of self-regulation.

The differences in patient and study characteristics are distinct and complicate direct comparison between the studies. For example, mean HbA1c ranges from 7.5% to 12%. Furthermore, timing and frequency of SMBG vary widely, some studies advise patients which values to strive for, some studies give advice how to achieve these goals, and in some studies patients receive additional help from a dietician or a diabetes specialist nurse. These large differences in study design illustrate the many different ways that SMBG is integrated in the management of noninsulin-treated patients with T2DM and make it almost impossible to draw a single overall conclusion about its effectiveness.

Regardless of the heterogeneity of the studies, it is remarkable that there is an inverse relationship between study quality on the one hand, and efficacy on glycemic control and quality of life parameters on the other. Only 1 study of high methodological quality found a significant improvement of HbA1c of 0.24% (95% CI 0.03, 0.45) with SMBG compared to control.Citation14 The other 4 well designed studies found no effects of SMBG on glycemic control, but did report a worsening of quality of life parameters compared to control.Citation11Citation13,Citation16,Citation17,Citation21 When comparing the study by Barnett et al with the other well designed studies in order to find a possible explanation for the differences in effects on HbA1c, no major differences were found for the interventions used. What was somewhat different in the study by Barnett et al is the shorter diabetes duration and the lower body mass index (BMI) of patients included ().

Two recent systematic reviews concluded that the effect of SMBG on HbA1c was on average 0.21% and 0.22%.Citation15,Citation22 One may question, however, whether it is justified to perform a meta-analysis including all the trials, keeping in mind that the benefits of SMBG were found primarily in low quality trials. A Cochrane review did not perform a meta-analysis because of the differences in study quality and because of the differences in baseline data of the patients and type of interventions between the studies.Citation4,Citation34

A collaboration of authors of previous trials will investigate whether a certain subgroup of patients can be found who might benefit more from SMBG than the effects found in the systematic reviews.Citation5 Perhaps, a short diabetes duration and a low BMI could be factors as hypothesized earlier. On top of that, a large RCT will be performed in the Netherlands including 600 patients with noninsulin-treated T2DM, in which the patients will be randomized into 3 groups: SMBG, self-measurement of urine glucose, and control.Citation35 Perhaps, these 2 studies will give some new perspectives about the usefulness of SMBG in certain subgroups of patients. Until then, we recommend that SMBG should not be used generally in a population of noninsulin-treated diabetic patients. Effectiveness on glycemic control has not been established, and quality of life could diminish.

Disclosure

The author report no conflicts of interest.

References

  • GoldsteinDELittleRRLorenzRATests of glycemia in diabetesDiabetes Care20042771761177315220264
  • NathanDMMcKitrickCLarkinMSchaffranRSingerDEGlycemic control in diabetes mellitus: have changes in therapy made a difference?Am J Med199610021571638629649
  • KarterAJAckersonLMDarbinianJASelf-monitoring of blood glucose levels and glycemic control: the Northern California Kaiser Permanente Diabetes registryAm J Med200111111911448654
  • WelschenLMBloemendalENijpelsGSelf-monitoring of blood glucose in patients with type 2 diabetes who are not using insulinCochrane Database Syst Rev2005182CD00506015846742
  • FarmerAJHeneghanCBarnettAHSelf-monitoring of blood glucose trialists collaboration. Individual patient data meta-analysis of trials of self-monitoring of blood glucose in noninsulin treated type 2 diabetes: Protocol for a systematic reviewPrim Care Diabetes Epub 2009 Apr 15
  • WingRREpsteinLHNowalkMPScottNKoeskeRHaggSDoes self-monitoring of blood glucose levels improve dietary compliance for obese patients with type II diabetes?Am J Med19868158308363535493
  • ScherbaumWAOhmannCAbholzHHDraganoNLankischMEffect of the frequency of self-monitoring blood glucose in patients with type 2 diabetes treated with oral antidiabetic drugs-a multi-centre, randomized controlled trialPLoS ONE200838e308718769484
  • JohnsonJAMajumdarSRBowkerSLTothELEdwardsASelf-monitoring in Type 2 diabetes: a randomized trial of reimbursement policyDiabet Med200623111247125117054603
  • SieboldsMGaedekeOSchwedesUSMBG Study GroupSelf-monitoring of blood glucose – psychological aspects relevant to changes in HbA1c in type 2 diabetic patients treated with diet or diet plus oral antidiabetic medicationPatient Educ Couns200662110411016159705
  • SchwedesUSieboldsMMertesGSMBG Study GroupMeal-related structured self-monitoring of blood glucose: effect on diabetes control in noninsulin-treated type 2 diabetic patientsDiabetes Care200225111928193212401734
  • FarmerAJWadeANFrenchDPDiGEM Trial GroupBlood glucose self-monitoring in type 2 diabetes: a randomised controlled trialHealth Technol Assess20091315iiiivixxi150
  • SimonJGrayAClarkePWadeANeilAFarmerADiabetes Glycaemic Education and Monitoring Trial GroupCost effectiveness of self monitoring of blood glucose in patients with noninsulin treated type 2 diabetes: economic evaluation of data from the DiGEM trialBMJ200833676541177118018420663
  • FarmerAWadeAGoyderEImpact of self monitoring of blood glucose in the management of patients with noninsulin treated diabetes: open parallel group randomised trialBMJ2007335761113217591623
  • BarnettAHKrentzAJStrojekKThe efficicay of self-monitoring of blood glucose in the management of patients with type 2 diabetes treated with a gliclazide modified release-based regimen. A multicentre, randomized, parallel-group, 6-month evaluation (DINAMIC-1 study)Diabetes Obes Metabol20081012391247
  • St. JohnADavisWAPriceCPDavisTMThe value of self-monitoring of blood glucose: a review of recent evidenceJ Diabetes Complications Epub 2009 Feb 19
  • AllenBTDeLongERFeussnerJRImpact of glucose self-monitoring on noninsulin-treated patients with type II diabetes mellitus. Randomized controlled trial comparing blood and urine testingDiabetes Care19901310104410502170088
  • DavidsonMBCastellanosMKainDDuranPThe effect of self monitoring of blood glucose concentrations on glycated hemoglobin levels in diabetic patients not taking insulin: a blinded, randomized trialAm J Med2005118442242515808142
  • FontbonneABillaultBAcostaMIs glucose self-monitoring beneficial in noninsulin-treated diabetic patients? Results of a randomized comparative trialDiabete Metab19891552552602630378
  • GuerciBDrouinPGrangéVASIA GroupSelf-monitoring of blood glucose significantly improves metabolic control in patients with type 2 diabetes mellitus: the Auto-Surveillance Intervention Active (ASIA) studyDiabetes Metab200329658759414707887
  • MuchmoreDBSpringerJMillerMSelf-monitoring of blood glucose in overweight type 2 diabetic patientsActa Diabetol19943142152197888692
  • O’KaneMJBuntingBCopelandMCoatesVEESMON study groupEfficacy of self monitoring of blood glucose in patients with newly diagnosed type 2 diabetes (ESMON study): randomised controlled trialBMJ200833676541174117718420662
  • TowfighARomanovaMWeinrebJESelf-monitoring of blood glucose levels in patients with type 2 diabetes mellitus not taking insulin: a meta-analysisAm J Manag Care200814746847518611098
  • McGeochGDerrySMooreRASelf-monitoring of blood glucose in type-2 diabetes: what is the evidence?Diabetes Metab Res Rev200723642344017538940
  • WelschenLMBloemendalENijpelsGFrom the Cochrane Library and Diabetes Care: self-monitoring of blood glucose probably an effective way to improve glycaemic control in patients with type 2 diabetes not taking insulinNed Tijdschr Geneeskd2006150331826182916967593
  • JansenJPSelf-monitoring of glucose in type 2 diabetes mellitus: a Bayesian meta-analysis of direct and indirect comparisonsCurr Med Res Opin200622467168116684428
  • SaudekCDDerrRLKalyaniRRAssessing glycemia in diabetes using self-monitoring blood glucose and hemoglobin A1c JAMA2006295141688169716609091
  • Home glucose monitoring makes little difference in type 2 diabetesJ Fam Pract2005541193616299946
  • WelschenLMBloemendalENijpelsGSelf-monitoring of blood glucose in patients with type 2 diabetes who are not using insulin: a systematic reviewDiabetes Care20052861510151715920083
  • SarolJN JrNicodemusNA JrTanKMGravaMBSelf-monitoring of blood glucose as part of a multi-component therapy among noninsulin requiring type 2 diabetes patients: a meta-analysis (1966–2004)Curr Med Res Opin200521217318415801988
  • HolmesVGriffithsPSelf-monitoring of glucose levels for people with type 2 diabetesBr J Community Nurs200271414611823730
  • CosterSGullifordMCSeedPTPowrieJKSwaminathanRSelf-monitoring in Type 2 diabetes mellitus: a meta-analysisDiabet Med2000171175576111131099
  • CosterSGullifordMCSeedPTPowrieJKSwaminathanRMonitoring blood glucose control in diabetes mellitus: a systematic reviewHealth Technol Assess2000412iiv193
  • FaasASchellevisFGVan EijkJTThe efficacy of self-monitoring of blood glucose in NIDDM subjects. A criteria-based literature reviewDiabetes Care1997209148214869283802
  • KleefstraNHouwelingSTvan BallegooieEBiloHJSelf-monitoring of blood glucose in patients with type 2 diabetes who are not using insulin: response to Welschen et alDiabetes Care20052810259616186317
  • MalandaULBotSDKostensePJSnoekFJDekkerJMNijpelsGEffects of self-monitoring of glucose in noninsulin treated patients with type 2 diabetes: design of the IN CONTROL-trialBMC Fam Pract20091012619397795