Type of test Blood

 Normal findings

 Blood:

 Adult/elderly: rise in plasma glucose levels > 20 mg/dL

No abdominal cramps or diarrhea

 Breath: < 50 ppm hydrogen increase over baseline

 Test explanation and related physiology

 This test is performed to detect lactose intolerance, intestinal malabsorption, maldigestion, or bacterial overgrowth in the small intestine. Because lactose-intolerant patients have an absence of lactase, any lactose (the common sugar in dairy products) ingested will not be digested in the small bowel. Thus the colon is flooded with a high lactose load. Although all adults have some degree of lactase reduction, severe lactose intolerance can occur in patients with inflammatory bowel disease, short gut syndrome, and other malabsorption syndromes. Lactase deficiency can be congenital and become apparent in newborns. These infants present with vomiting, diarrhea, malabsorption, and failure to thrive.

In this test, the patient is given an oral lactose load. If lactase is not present in sufficient quantities, lactose is not metabolized to glucose and galactose. Plasma levels of glucose do not rise as expected. Therefore lower than expected serum glucose levels suggest intestinal lactase deficiency. Patients who have malabsorption without lactase deficiency also fail to elevate the blood glucose levels.

There is a breath-test portion of this diagnostic test in which exhaled air is analyzed for hydrogen content. This is called the lactose breath test (or hydrogen breath test). The bacteria in the colon produce hydrogen when exposed to unabsorbed food, particularly the lactose load that was not absorbed in the small intestine. Large amounts of hydrogen may also be produced when the colonic bacteria move back into the small intestine, a condition called bacterial overgrowth of the small bowel. In this instance the overgrowth bacteria are exposed to the lactose load that has not had a chance to completely traverse the small intestine to be fully digested and absorbed. Large amounts of the hydrogen produced by the bacteria are absorbed into the blood flowing through the wall of the small intestine and colon. This hydrogen-containing blood travels to the lungs, where the hydrogen is released and exhaled in the breath in measurable quantities.

Before lactose hydrogen breath testing, individuals must fast for at least 12 hours. At the start of the test, the individual blows into a hydrogen analyzer. The individual then ingests a small amount of the test sugar (e.g., lactose, sucrose, sorbitol, fructose, or lactulose, depending on the purpose of the test). Additional samples of breath are collected and analyzed for hydrogen every 15 minutes for 1 to 5 hours. When rapid intestinal transit is present, the test dose of nondigestible lactulose reaches the colon more quickly than normal; therefore hydrogen is produced by the colonic bacteria soon after the sugar is ingested. When bacterial overgrowth of the small bowel is present, ingestion of lactulose results in two separate periods during the test in which hydrogen is produced: an earlier period caused by the bacteria in the small intestine and a later one caused by the bacteria in the colon.

More recently, lactose (and other disaccharidases) deficiency can be detected by identifying the disaccharidase in the tissue of the colon, obtained by colonoscopy. For example, if the test shows less than 10.0 µmol/min of lactase per gram of protein, the patient has lactase insufficiency. Maltase, palatinase, and sucrase deficiencies can also be evaluated with this technique.

Interfering factors

 • Enterogenous steatorrhea

 • Strenuous exercise

 • Smoking may increase blood glucose levels.

 • Ethnicity has a major effect on primary lactose deficiency.

 • Patients with diabetes may have glucose levels that exceed 20 mg/dL despite lactase insufficiency.

* Antibiotics can decrease the bacteria in the intestine and may cause false-negative breath tests and thus should not be taken for 1 month before testing.

 Procedure and patient care

 Before

* Explain the procedure to the patient. Inform the patient that four blood samples will be needed.

* Instruct the patient to fast for 12 hours before testing.

* Instruct the patient to avoid strenuous exercise for 8 hours before testing because exercise may factitiously affect the blood glucose level.

* Inform the patient that smoking is prohibited for approximately 8 hours before testing because smoking can increase the blood glucose level.

During

 • Collect a venous blood sample in a gray-top tube from the fasting patient.

• Provide a specified dose of lactose for the patient. Usually dilute 50 to 100 g of lactose with 200 mL of water for ingestion in adults.

• Note that pediatric doses of lactose are based on weight.

 • Collect three more blood samples at 30, 60, and 120 minutes after the ingestion of lactose.

* Tell the patient that the only discomfort is the venipuncture; however, patients with lactase deficiency may have symptoms of lactose intolerance (e.g., cramps and diarrhea).

 • If the breath test is being done, the exhaled air is evaluated for hydrogen content before ingestion of lactose and every 15 minutes thereafter. Hydrogen levels are recorded.

 After

 • Apply pressure to the venipuncture site.

 • Note that patients with abnormal test results may receive a monosaccharide tolerance test (e.g., glucose or galactose tolerance test).

Abnormal findings

 Decreased levels

- Lactase insufficiency

- Intestinal malabsorption or maldigestion

- Small bowel overgrowth of bacteria

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم المشاريع ينتهي من نصب شاشات عرض في باب القبلة والصحن الشريف استعدادًا لمراسم تبديل الراية

جامعة الكفيل تنشر لافتات السواد استعدادًا لاستقبال شهر المحرّم الحرام

استعدادًا لشهر المحرم الحرام.. قسم الصيانة ينهي أعمال صيانة الإنارة الخاصة بالصحن الشريف وتبديلها

قسم الشؤون الفكرية يقيم ندوة علمية حول إسهامات العتبة العباسية المقدسة في تطوير البحث الأكاديمي في نيجيريا

المزيد

الآخبار الصحية

دراسة تكشف علاقة خطيرة بين عمر الأم وصحة مولودها

دراسة تحذر.. اضطراب نوم بسيط قد يسبب الموت المبكر ؟

الاستحمام بالماء الساخن.. راحة مؤقتة وأضرار دائمة للبشرة

ماذا يحدث للجسم عند تخطي وجبة الإفطار؟

المزيد

الآخبار التكنلوجية

كيف تساعد الصيانة الوقائية في الحفاظ على كفاءة التكييف في سيارتك ؟

في ظاهرة غريبة حيرت العلماء.. كوكبنا قد يسجل أقصر يوم في التاريخ هذا الصيف!

السد الصيني العملاق يعيق دوران الأرض ويغيّر شكلها ؟

السعودية تطلق 10 تجارب علمية إلى محطة الفضاء الدولية

المزيد

مواضيع ذات صلة

Lactoferrin

lactic dehydrogenase (LDH, Lactate dehydrogenase)

lactic acid (Lactate)

ischemia-modified albumin (IMA)

iron level and total iron-binding capacity (Fe and TIBC, Transferrin saturation, Transferrin)

Platelet Indices and Platelet Count

Red Cell Distribution

Flow Cytometry

intrinsic factor antibody (IF ab)

insulin-like growth factor (IGF-1, Somatomedin C, Insulin-like growth factor binding proteins [IGF BP])

insulin assay

immunoglobulin quantification