Glucose Tolerance Test (GTT) 2-Hour Collection Instructions

Principle

Diabetes mellitus is a group of metabolic disorders = with one common manifestation: hyperglycemia. Chronic hyperglycemia causes damag= e to the eyes, kidneys, nerves, heart and blood vessels. Screening for diabetes mellitus should begin at 45 years of age and should be repeated every three years in persons without risk factors, and should begin earlier and be repe= ated more often in those with risk factors. Risk factors include:

· obesity

· first-degree relatives with diabetes mellitu= s

· hypertension

· hypertriglyceridemia

· previous evidence of impaired glucose homeostasis.

Safety

To minimize the risk of accidental exposure, Univers= al Precautions and all safety policies should be followed when handling biolog= ical specimens. This includes the = use of personal protective equipment such as gloves, lab coats, face protection (w= hen necessary), and biowipes when performing laboratory testing.

Patient Preparation

The GTT should be administered in the morning after = the patient has had at least 3 days of an unrestricted diet (>150 g carbohydrates daily) and usual physical activity.

The patient should be fasting for at least 8 hours p= rior to the test, during which the patient may drink water only. The patient sho= uld not exercise during this fast.

The patient should be seated comfortably during the = test. The patient should remain inactive and take nothing by mouth (including tobacco) during the test period. Only small sips of water and ice are permissible during testing.

Inform patient that specimens will be drawn at timed intervals following the glucose dosage.&nb= sp;

Specimens

Heparinized plasma (preferred) or serum.

Glucose Tolerance Beverage Dosage

Glucose Tolerance Beverage (Dexicola) 100g glucose/10 ounces:

Adults, non-pregnant: 7.5 ounces (75g of glucose)

Children: Find child’s weight on chart to determine appropriate dose.

Pediatric dosing is ba= sed on 1.75g glucose/kg body weight and should not to exceed 75g of glucose. See chart below:

Pediatric Glucose Dosage Chart

Bo= dy Weight	Do= sage – 100g bottle
lb	Kg	oz	mL
20	9.1	1.6	47
25	11.4	2.0	59
30	13.6	2.4	71
35	15.9	2.8	82
40	18.2	3.2	94
45	20.5	3.6	106
50	22.7	4.0	118
55	25.0	4.4	130
60	27.3	4.8	141
65	29.5	5.2	153
70	31.8	5.6	165
75	34.1	6.0	177
80	36.4	6.4	188
85	38.6	6.8	200
90	40.9	7.2	212
94+	42.7+	7.5	221

Specimen Collection Procedure

1.&n= bsp; Order a GTT, 2HR in PathNet. This will generate labels for a GL= U F and GLU 2 H.

2.&n= bsp; Print a copy of the Glucose Test Result Interpretation (in Lab Help Interpretative Information) for the patient to read.

3.&n= bsp; Obtain the fasting blood specimen and send to the lab STAT

4.&n= bsp; A chemistry tech will evaluate the fasting b= lood glucose level and notify the testing center as to whether they may proceed = with the test or allow the patient to leave.

· If the fasting blood level is 126 mg/dL or l= ess, continue the test. See step (= 4.)

· If the level is greater than 126 mg/dL, info= rm MOB that the GTT has been completed and that the patient is not to be given the glucose toler= ance beverage.

5.&n= bsp; Give the adult non-pregnant patient a standa= rd dose of 75 gm dose of Dexicola (appropriate amount is removed from a 100 g dose bottle). For children weighing less than 94 lbs refer to the Pediatric Gluc= ose Dosage chart in the Glucose Tolerance Beverage Dose section of this procedu= re.

6.&n= bsp; Instruct the patient to drink the dose withi= n 5 minutes and record the time of intake completion.

7.&n= bsp; Obtain a second blood specimen at 2 hours fr= om the time the glucose loading dose is given. Label with the appropriate PathNet= label and send to the lab ASAP.

Procedural Notes

1. Patient reactions are not unc= ommon with the glucose tolerance test. These reactions may include nausea, vomiti= ng, fainting or sweating. If a reaction occurs, make the patient as comfortable= as possible. Notify a Supervisor, charge person, the Emergency Department physician or pathologist.

2.&nbs= p; Many drugs may interfere with the test results if taken within 3 days of testing. Possible interfering drugs include: thiazide diuretics, beta-blockers, oral contraceptives, corticosteroids and some psychiatric medications.

3.&nbs= p; Extended glucose tolerance tests are no longer indicated. Contact the pathologist for additional information if necessary.

4. Reasons for invalid results i= nclude emesis and conditions which delay stomach emptying.

Document Control

Facility: Central Maine Med= ical Center, 300 Main Street, Lewiston, Maine&n= bsp; 04240

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