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Diagnostic Tests for Diabetes

Contents
  1. Diabetes: Introduction
  2. Tests for Diabetes
  3. Symptoms of Diabetes
  4. Diagnosis
  5. Home Diagnostic Testing
  6. Failure to Diagnose
  7. Alternative Diagnoses
  8. Misdiagnosis
  9. Complications

Diabetes: Diagnostic Tests

The list of diagnostic tests mentioned in various sources as used in the diagnosis of Diabetes includes:

Diabetes Tests: Book Excerpts

Home Diagnostic Testing

These home medical tests may be relevant to Diabetes:

Diabetes Diagnosis: Book Excerpts

Tests and diagnosis discussion for Diabetes:

Diabetes Overview: NIDDK (Excerpt)

The fasting plasma glucose test is the preferred test for diagnosing type 1 or type 2 diabetes. However, a diagnosis of diabetes is made for any one of three positive tests, with a second positive test on a different day:

  • A random plasma glucose value (taken any time of day) of 200 mg/dL or more, along with the presence of diabetes symptoms.

  • A plasma glucose value of 126 mg/dL or more, after a person has fasted for 8 hours.

  • An oral glucose tolerance test (OGTT) plasma glucose value of 200 mg/dL or more in the blood sample, taken 2 hours after a person has consumed a drink containing 75 grams of glucose dissolved in water. This test, taken in a laboratory or the doctor's office, measures plasma glucose at timed intervals over a 3-hour period.

Gestational diabetes is diagnosed based on plasma glucose values measured during the OGTT. Glucose levels are normally lower during pregnancy, so the threshold values for diagnosis of diabetes in pregnancy are lower. If a woman has two plasma glucose values meeting or exceeding any of the following numbers, she has gestational diabetes: a fasting plasma glucose level of 95 mg/dL, a 1-hour level of 180 mg/dL, a 2-hour level of 155 mg/dL, or a 3-hour level of 140 mg/dL. (Source: excerpt from Diabetes Overview: NIDDK)

Am I at Risk for Type 2 Diabetes: NIDDK (Excerpt)

If you are 45 years old or older, you need to get tested for diabetes, even if you do not have any of the risk factors listed below. If you are younger than 45 and have one or more risk factors, you should also get tested. Ask your doctor for a fasting blood glucose test. The results of this blood test will tell your doctor how much glucose is in your blood. Your doctor may ask you to have the test twice.

Even if your blood glucose level is normal and you have no risk factors, if you are over 45, you may need to remind your doctor to check your blood glucose again in 3 years. If you have at least one of the risk factors below, have your blood checked more frequently. (Source: excerpt from Am I at Risk for Type 2 Diabetes: NIDDK)

Diabetes Diagnosis: NIDDK (Excerpt)

A Lower Number To Diagnose Diabetes The expert committee also recommended a lower fasting plasma glucose (FPG) value to diagnose diabetes. The new FPG value is 126 milligrams per deciliter (mg/dL) or greater, rather than 140 mg/dL or greater. This recommendation was based on a review of the results of more than 15 years of research. This research showed that a fasting blood glucose of 126 mg/dL or greater is associated with an increased risk of diabetes complications affecting the eyes, nerves, and kidneys. When diagnosis was based on a blood glucose value of 140 mg/dL or greater, these complications often developed before the diagnosis of diabetes. The experts believe that earlier diagnosis and treatment can prevent or delay the costly and burdensome complications of diabetes.

The prior criteria for diagnosing diabetes relied heavily on performing an oral glucose tolerance test (OGTT). In this test, the person must come in fasting, drink a glucose syrup, and have a blood sample taken 2 hours later. This complicated procedure made detection and diagnosis of diabetes a difficult and cumbersome process, and the expert committee recommended that it be eliminated from clinical use. The change to using fasting plasma glucose for determining the presence of diabetes will make detection and diagnosis of diabetes more routine. The fasting value can be easily obtained during routine physician visits, in clinics at the place of employment, and other situations. Currently, about 5 to 6 million adults in the United States have diabetes but do not know it. The simpler testing method of measuring fasting glucose should help identify these people so they can benefit from treatment sooner. (Source: excerpt from Diabetes Diagnosis: NIDDK)

Diabetes Diagnosis: NIDDK (Excerpt)

The committee states that diabetes can be detected by any of three positive tests. To confirm the diagnosis, there must be a second positive test on a different day.

  • A casual plasma glucose level (taken at any time of day) of 200 mg/dL or greater when the symptoms of diabetes are present.

  • A fasting plasma glucose value of 126 mg/dL or greater.

  • An OGTT value in the blood of 200 mg/dL or greater measured at the 2-hour interval.

As mentioned above, the committee recommended that the OGTT not be used. (Source: excerpt from Diabetes Diagnosis: NIDDK)

Diabetes Statistics in the United States: NIDDK (Excerpt)

The new diagnostic criteria for diabetes include the following changes:

  • The routine diagnostic test for diabetes is now a fasting plasma glucose test rather than the previously recommended oral glucose tolerance test. (However, in certain clinical circumstances, physicians may still choose to perform the oral glucose tolerance test.)

  • A confirmed** fasting plasma glucose value of greater than or equal to 126 milligrams/deciliter (mg/dL) indicates a diagnosis of diabetes. Previously, a value of greater than or equal to 140 mg/dL had been required for diagnosis.

  • In the presence of symptoms of diabetes, a confirmed** nonfasting plasma glucose value of greater than or equal to 200 mg/dL indicates a diagnosis of diabetes.

  • When a doctor chooses to perform an oral glucose tolerance test (by administering 75 grams of anhydrous glucose dissolved in water, in accordance with World Health Organization standards, and then measuring the plasma glucose concentration 2 hours later), a confirmed** glucose value of greater than or equal to 200 mg/dL indicates a diagnosis of diabetes.

In pregnant women, different requirements are used to identify the presence of gestational diabetes.

*For further information about the new diagnostic criteria for diabetes, please see the "Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus," in the References.

**Except in certain specified circumstances, abnormal tests must be confirmed by repeat testing on another day. (Source: excerpt from Diabetes Statistics in the United States: NIDDK)

Medicines for People With Diabetes: NIDDK (Excerpt)

One other number to know is the result of a blood test your doctor does called hemoglobin A-1-c (HE-muh-glow-bin A-1-C) or glycated hemoglobin (GLY-kay-ted HE-muh-glow-bin). It shows your blood glucose control during the past 2 to 3 months. For most people, a good hemoglobin A-1-c is 7 percent. (Source: excerpt from Medicines for People With Diabetes: NIDDK)

Keep your kidneys healthy: NIDDK (Excerpt)

Each year make sure your doctor tests a sample of your urine to see if your kidneys are leaking albumin. If your kidneys are not leaking a lot of albumin, ask your doctor to check your urine for even smaller amounts of albumin. This is called microalbumin (MY-kro-al-BYOO-min). (Source: excerpt from Keep your kidneys healthy: NIDDK)

Keep your kidneys healthy: NIDDK (Excerpt)

Your doctor might test your blood to measure the amounts of creatinine (kree-AT-ih-nin) and urea (yoo-REE-uh). These are waste products your body makes. If your kidneys are not cleaning them out of your blood, they can build up and make you sick.

Your doctor might also ask you to collect your urine in a large container for a whole day or just overnight. (Source: excerpt from Keep your kidneys healthy: NIDDK)

Diabetes: NWHIC (Excerpt)

A diagnosis of diabetes can be confirmed by a series of tests that might include:

  • A blood test that measures the glucose in your blood. A blood glucose level of 200 milligrams per deciliter (mg/dL) or greater, with symptoms, means that you have diabetes.

  • A blood test for glucose after you have fasted, called fasting plasma glucose (FPG) value. An FPG value of 126 mg/dL or greater means that you have diabetes.

  • A measurement of glucose in your blood through an oral glucose tolerance test (OGTT). Although this test is no longer recommended because it is cumbersome, some health care providers may still use it. After fasting, you have to drink a glucose syrup and have a blood sample taken 2 hours later. An OGTT value of 200 mg/dL or greater means that you have diabetes.

(Source: excerpt from Diabetes: NWHIC)

Diagnosis of Diabetes: medical news summaries:

The following medical news items are relevant to diagnosis of Diabetes:

Diagnostic Tests for Diabetes: Online Medical Books

16 MEDICAL BOOKS ONLINE! Review excerpts from medical books online, free, without registration, for more information about the diagnostic tests for Diabetes.

GLYCOSURIA: DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)

The investigation of glycosuria should include a glucose tolerance test, chemistry panel, and electrolyte panel. If there are clinical features of an endocrine disorder, the various tests for these disorders should be ordered.

 

» READ BOOK EXCERPT ONLINE »

Source: Algorithmic Diagnosis of Symptoms and Signs, 2003

HYPERGLYCEMIA: DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)

Further workup may include a CBC, urinalysis, chemistry panel, glucose tolerance test, plasma cortisol, free T 4 , TSH, plasma and urine catecholamines, skull x-ray, vanillylmandelic acid (VMA) , and endocrinology consult.

 

» READ BOOK EXCERPT ONLINE »

Source: Algorithmic Diagnosis of Symptoms and Signs, 2003

POLYDIPSIA: DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)

The basic workup includes a CBC, sedimentation rate, urinalysis, 24-hr urine volume, a serum and urine osmolality, a thyroid profile, and x-rays of the skull and long bones.

The diagnosis of hyperparathyroidism may be assisted by ordering a serum parathyroid hormone level. Also, a 24-hr urine collection for calcium may be done to help diagnose this condition. Microscopic examination of the urinary sediment will help diagnose renal disease, as will renal biopsies. If pituitary diabetes insipidus is suspected, a CT scan of the brain and blood tests for serum growth hormone, FSH, LH, ACTH, and TSH may be done. The Hickey-Hare test and monitoring intake and output before and after vasopressin (Pitressin®) will be useful in differentiating pituitary diabetes insipidus from nephrogenic diabetes insipidus. The concentrations of circulating vasopressin may be measured by immunoassay.

An endocrinologist should be consulted before ordering these expensive diagnostic tests.

 

» READ BOOK EXCERPT ONLINE »

Source: Algorithmic Diagnosis of Symptoms and Signs, 2003

Polydipsia: History and physical examination
(Handbook of Signs & Symptoms (Third Edition))

Obtain a history. Find out how much fluid the patient drinks each day. How often and how much does he typically urinate? Does the need to urinate awaken him at night? Determine if he or anyone in his family has diabetes or kidney disease. What medications does he use? Has his lifestyle changed recently? If so, have these changes upset him?

If the patient has polydipsia, take his blood pressure and pulse when he’s in supine and standing positions. A decrease of 10 mm Hg in systolic pressure and a pulse rate increase of 10 beats/
minute from the supine to the sitting or standing position may indicate hypovolemia. If you detect these changes, ask the patient about recent weight loss. Check for signs of dehydration, such as dry mucous membranes and decreased skin turgor. Infuse I.V. replacement fluids, as needed.

» READ BOOK EXCERPT ONLINE »

Source: Handbook of Signs & Symptoms (Third Edition), 2006

Polydipsia: History and physical examination
(Professional Guide to Signs & Symptoms (Fifth Edition))

Obtain a history. Find out how much fluid the patient drinks each day. How often and how much does he typically urinate? Does the need to urinate awaken him at night? Determine if he or anyone in his family has diabetes or kidney disease. What medications does he use? Has his lifestyle changed recently? If so, have these changes upset him?

If the patient has polydipsia, take his blood pressure and pulse when he’s in supine and standing positions. A decrease of 10 mm Hg in systolic pressure and a pulse rate increase of 10 beats/minute from the supine position to the sitting or standing position may indicate hypovolemia. If you detect these changes, ask the patient about recent weight loss. Check for signs of dehydration, such as dry mucous membranes and decreased skin turgor. Infuse I.V. replacement fluids as needed.

» READ BOOK EXCERPT ONLINE »

Source: Professional Guide to Signs & Symptoms (Fifth Edition), 2006

Polydipsia: Physical examination
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)

 A thorough general physical examination, including vital signs, is helpful in making the diagnosis, but the emphasis is on the neurologic examination (i.e., visual fields, cranial nerve deficits, oculomotor palsies, and reflexes). Signs of recent weight loss or presence of peripheral neuropathy is helpful in making the diagnosis of DM (Chapters 2.13 and 4.6).

Testing

A. Clinical laboratory tests. A urinalysis needs to be performed to look for glucosuria of DM or the low specific gravity associated with DI. A chemistry panel is helpful in checking for elevated serum glucose levels of DM or an elevated creatinine seen with renal disease or nephrogenic DI. A calcium level could be useful if hypercalcemia is suspected (Chapter 17.4). Serum and urine osmolality are useful in differentiating between DI, which presents with increased serum osmolality and in an appropriately low urine osmolality (specific gravity < 1.005), and excessive water intake, which presents with low or normal serum osmolality and an appropriately low urine osmolality. Normal serum values are between 285 and 295 mOsm/L.

B. Diagnostic imaging. Magnetic resonance imaging (MRI) of the head may be indicated to exclude pituitary or hypothalamic tumors. In neurogenic DI, MRI is quite specific because the normal bright spot of a functioning pituitary gland will be absent (3).

C. Water deprivation test. This indirect test may be useful in making the diagnosis of DI and to differentiate between neurogenic and nephrogenic DI by determining the effects of water deprivation (mild dehydration) on ADH secretion by measuring serum, urine osmolality, urine-specific gravity, and serum sodium in a controlled environment (3). This test needs to be carefully supervised by someone able to treat severe hypertonic dehydration if necessary. Patients with mild polydipsia are placed on fluid restriction starting at midnight prior to testing, but fluids are restricted in those with severe polydipsia during the day only. Baseline body weight, plasma osmolarity, serum sodium, and urine osmolarity are determined. Urine osmolarity and weight are assessed on an hourly basis. Adequate dehydration is noted by a decrease in body weight by 5% and serum osmolarity by more than 275 mOsm/L. A normal response would show normal plasma osmolarity and sodium concentration with decreased urine output and increasing urine osmolarity to more than 800 mOsm/L (i.e., two to four times greater than the plasma). In contrast to healthy patients, patients with DI cannot concentrate their urine in response to dehydration. Patients with central DI respond to desmopressin (a synthetic analog of vasopressin) administered intranasally, whereas patients with nephrogenic DI do not (4). Sometimes patients do not fall into definite categories (e.g., partial central DI). The direct form of testing where ADH levels are measured after infusing hypertonic saline is rarely performed.

Diagnostic assessment

 Often important clues about the cause of polydipsia can be obtained with a directed clinical history with particular attention paid to the onset of symptoms, the presence of nocturia, and the medication history. The value of the physical examination is limited unless signs are evident of defects caused by a pituitary tumor (e.g., progressive headaches, visual field defects) or endocrinologic symptoms (e.g., amenorrhea, galactorrhea, acromegaly, Cushing’s disease). Often the diagnosis is made with routine laboratory tests. Sometimes a water deprivation test needs to be performed to make the diagnosis, but this test should be done in a hospital setting with the patient monitored closely for dehydration.


References

1. Greendyke RM, Bernhardt AJ, Tasbas HE. Polydipsia in chronic psychiatric patients. Neuropsychopharmacology 1998;18:272–281.

2. Olpade-Olaopa EO, Morley RN, Ahiaku ER, Bramble FJ. Iatrogenic polydipsia: a rare cause of water intoxication in urology. Br J Urol 1997;7:488.

3. Adam P. Evaluation and management of diabetes insipidus. Am Fam Physician 1997;55:2146–2153.

4. Blevins LS Jr, Wand GS. Diabetes insipidus. Crit Care Med 1992;20:69–79.>>

» READ BOOK EXCERPT ONLINE »

Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000

Diabetes Mellitus: Physical examination
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)

Patients often present with similar physical findings in both type 1 and type 2 DM, owing to hyperglycemia. In the young child, failure to grow and gain weight can occur with type 1 DM. The child may be ill appearing, lethargic, and often have signs of dehydration (tachypnea, tachycardia, and low blood pressure). Ketone production will produce a fruity odor on the patient’s breath. The patient with type 2 DM tends to be obese (especially upper body obesity) and may appear fatigued and have muscle weakness or decreased vision. The neurologic examination may reveal painful feet and numbness. Monilial infections may be found in the vagina and pubic areas.

Testing

A. Type 1 diabetes. Not all children with hyperglycemia have diabetes. Some children with a severe illness (e.g., severe dehydration from diarrhea or asthma treated with corticosteroids) may have elevated serum glucose and ketosis. If the diagnosis is uncertain, a low serum insulin level along with hyperglycemia supports the diagnosis of DM and excludes all other diagnoses. Elevated glycosylated hemoglobin provides a strong circumstantial case for the diagnosis of DM, but it is not used alone for the diagnosis. Performing a glucose tolerance test is rarely necessary. However, it is imperative to obtain insulin levels along with the blood glucose values when it is performed.

B. Type 2 diabetes. The American Diabetes Association (ADA) diagnostic criteria for type 2 DM are either (a) symptoms of diabetes and a casual plasma glucose level of 200 mg/dl or greater, (b) a fasting plasma glucose level of 126 mg/dl or greater, or (c) a plasma glucose level of 200 mg/dl or greater 2 hours after an oral glucose load (75 g). A “casual” plasma blood glucose level is obtained at any time of the day without regard to the time of the last meal, and a “fasting” level is obtained after a fast of at least 8 hours. If the only criterion is hyperglycemia, confirmation should be made on a different day (1).

Diagnostic assessment

 The presence of polyuria, polydipsia, polyphagia, and weight loss along with hyperglycemia and ketosis are sufficient to establish the diagnosis of type 1 DM. This provides an ample basis for beginning insulin therapy. Hyperglycemia can also occur during a severe illness. Therefore, the diagnosis of type 1 DM is not always clear. Low insulin levels may be needed to make the diagnosis. The key to the diagnosis of type 2 DM is the detection of hyperglycemia. Patients with symptoms of diabetes should have testing according to the ADA recommendations. Once the diagnosis is made, formulate a treatment program with the patient.


References

1. American Diabetes Association. Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 1997;20:1183–1197.

2. National Diabetes Data Group. Diabetes in America, 2nd ed. Bethesda, MD: National Institute of Diabetes and Digestive and Kidney Diseases, 1995. NIH publication 1468-1995.

3. Baker JR. Autoimmune endocrine disease. JAMA 1997;278:1931–1937.

» READ BOOK EXCERPT ONLINE »

Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000

Polydipsia: Physical assessment
(Signs & Symptoms: A 2-in-1 Reference for Nurses)

If the patient has polydipsia, take his blood pressure and pulse when he’s in supine and standing positions. A decrease of 10 mm Hg in systolic pressure and a pulse rate increase of 10 beats/minute from the supine to the sitting or standing position may indicate hypovolemia. If you detect these changes, ask the patient about recent weight loss. Check for signs of dehydration, such as dry mucous membranes and decreased skin turgor. Infuse I.V. replacement fluids as needed.

» READ BOOK EXCERPT ONLINE »

Source: Signs & Symptoms: A 2-in-1 Reference for Nurses, 2007

Polyuria and Polydipsia: Diagnostic Approach
(The Diagnostic Approach to Symptoms and Signs in Pediatrics)

  • Polyuriamust be distinguished from small volume urinary frequency, whichis common in pediatric practice. Children with polyuria often havenocturia and are unable to sleep through the night without wakingup to urinate. Most children with urinary frequency do not havepolyuria or a defect in urinary concentrating ability. Common causesof isolated urinary frequency are habit, attention-seeking behavior,and urinary tract infection.
  • Random sample of urine with specificgravity of >1.028 and absence of polyuria rules out a concentrationdefect. Even urinary specific gravity of >1.020 on randomor early morning sample indicates sufficient urinary concentrationsuch that symptomatic diabetes insipidus is unlikely. Children whohave urine with a somewhat lower than normal specific gravity butwho can sleep through the night without passing urine do not needfurther evaluation.
  • Presence of polyuria, dehydration,and high urinary specific gravity is evidence for osmotic diuresis,which is most commonly caused by diabetes mellitus. Dilute urineassociated with polyuria suggests diabetes insipidus or psychogenicpolydipsia. If blood glucose and urea nitrogen are normal, high serumosmolality with hyposmolar urine suggests ADH deficiency or resistance.Low serum osmolality with hyposmolar urine suggests primary polydipsia.
  • With either ADH deficiency or resistance,urine specific gravity rarely exceeds 1.005 and urinary osmolalityrarely exceeds 200 mOsm/kg. Water deprivation test thatdemonstrates inability to concentrate urine indicates diabetes insipidusand distinguishes it from primary polydipsia. If urine remains hypotonicwith dehydration, next step is to determine response to exogenousvasopressin, which distinguishes ADH deficiency from resistance.With ADH deficiency, administration of vasopressin causes diminishingof symptoms and increase in urine specific gravity, whereas no responseoccurs with ADH resistance.
  • With suspected renal disease, certaintests should be performed: CBC and differential; UA; urine culture;serum electrolytes, calcium, phosphorus, and creatinine; blood ureanitrogen; hemoglobin electrophoresis; and renal U/S. Othertests (e.g., determination of serum and urinary amino acids, voiding cystourethrography,and renal biopsy) may be necessary to define specific renal abnormality.
  • Psychosocial history of emotional disturbance,including episodes of compulsive water drinking and formation ofconcentrated urine with fluid deprivation, are evidence for psychogenicpolydipsia. This disorder may sometimes be difficult to distinguishfrom hypothalamic thirst defect, and consultation with a pediatricendocrinologist is recommended.

    • » READ BOOK EXCERPT ONLINE »

    Source: The Diagnostic Approach to Symptoms and Signs in Pediatrics, 2006

    Polydipsia: History and physical examination
    (Nursing: Interpreting Signs and Symptoms)

    Obtain a medical history. Find out how much fluid the patient drinks each day. How often and how much does he typically urinate? Does the need to urinate awaken him at night? Determine if he or anyone in his family has diabetes or kidney disease. What medications does he use? Has his lifestyle changed recently?

    If the patient has polydipsia, take his blood pressure and pulse when he's in supine and standing positions. A decrease of 10 mm Hg in systolic pressure and a pulse rate increase of 10 beats/minute from the supine to the sitting or standing position may indicate hypovolemia. Ask the patient about recent weight loss. Check for signs of dehydration, such as dry mucous membranes and decreased skin turgor.

    » READ BOOK EXCERPT ONLINE »

    Source: Nursing: Interpreting Signs and Symptoms, 2007


     » Next page: Diagnosis of Diabetes

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