Chronic Diabetes Case F Gestational Diabetes Mellitus (GDM) Clinical Pathology B Hoa Nguyen Tuan Anh Tran Thi Thuy Duong Trang

Objectives Explain the tests which may have been used in the diagnosis of GDM Role of self-monitoring blood glucose levels in patients with GDM Examine various approaches to use in blood glucose monitoring devices Accuracy and factors which affect the accuracy of these devices Processes required to give patients confidence in the result obtained

What is gestational diabetes? Carbohydrate/glucose intolerance of variable severity Asymptomatic Onset or first recognised during pregnancy

Tests may have been used in diagnosis of GDM Oral glucose tolerance test Urine glucose test Blood glucose test

Oral glucose tolerance test Measure the body’s ability to metabolise glucose Used to screen pregnant women for GDM between 24 and 28 weeks of pregnancy

Oral glucose tolerance test Fasting 8-12 hours (overnight) Patient’s blood sample collected Patient given a concentrated 75g load glucose drink Collect blood sample after 1 hour Collect blood sample after 2 hours

Target for oral glucose tolerance test If any 2 values are met or exceed, the diagnosis is GDM If 1 value is met or exceeded, the diagnosis is impaired glucose tolerance of pregnancy Fasting<5.5mmol/L 1 hour<8.0mmol/L 2 hours<7.0mmol/L

Blood glucose test Measure glucose level in the blood Blood sample withdrawn from patient and sent to laboratory for testing Target <5.5mmol/L Generally give first indication of diabetes not diagnosis

Urine glucose test Measure glucose level in the urine Urine sample collected and analysed by a dye or dipstick test Not as effective or precise as blood test because don’t see glucose in urine below a certain threshold eg. blood level of 8.8mmol/L

Reference ranges for urine glucose test Glucose Oxidase Phenylaminophenazone (end point) mg/L Glucose Oxidase Phenylaminophenazone (kinetic reaction) mg/L Oxygen rate- glucose oxidase mg/L Hexokinase endpoint mg/L

Role of monitoring blood glucose in GDM Self monitoring of blood glucose in GDM is crucial Once diagnosed, daily monitoring includes:  at least one fasting and  1 or 2 hours postprandial The frequency may be decreased or increased depending on result and stage of pregnancy

Targets for glycaemic control Fasting capillary (venous plasma) level < 5.5mmol/L 1 hour postprandial capillary (venous plasma) level < 8.0mmol/L 2 hour postprandial capillary (venous plasma) level < 7.0mmol/L

Various approaches to blood glucose monitoring Many methods and devices available Most common requires blood sample eg. fingerstick method:  finger pricked using lancet  blood placed on strip  strip placed in monitor to be measure

Problem Invasive Painful Inconvenient Provides only snapshot

Newer devices less invasive Uses electrical current to measure glucose levels Can be placed anywhere on the body Provides continuous and automatic monitoring

Glucose Monitoring Devices One Touch Ultra (LifeScan) FreeStyle (TheraSense) Accu-Chek Complete (MediSense; Abbott Labs) Ascencia Elite (Bayer)

Differences between devices Sizes Length of time for results Amount of blood needed Cleaning requirements Data management

Meter accuracy No standards for meter accuracy and precision Diabetes control and complications trial (DCCT) total errors of 20% or less is acceptable (not codified) International organisation for standardisation (ISO) require 20% maximum system error

Factors affect accuracy Altitude Hematocrit levels Ascorbic acid (vitamin C) Bilirubin Creatinine Acetaminophen (Tylenol) Urea

Accuracy of continuous blood glucose monitor eg. GlucoWatch Clinical study published in Nature Medicine indicates accuracy of GlucoWatch  Correlation coefficient = 0.90  Mean absolute error = 0.20  Mean bias 5.0%

GlucoWatch Accuracy and precision are not affected by:  Physiological factors age, race, gender, BMI…  Environmental factors Temperature, perspiration…  Other drugs used

Patient confidence Liquid control solutions Most companies are constantly trying to improve their products New approach to blood glucose monitoring provide continuous data Better treatment plan and confidence for patients