Lactase Enzyme Deficiency, Lactose Intolerance

Lactase Enzyme Deficiency

What samples are needed to detect Lactase enzyme deficiency?

1. Most tests available to diagnose lactase enzyme deficiency are done on stool.
2. The blood sample is needed to estimate blood glucose levels.
3. Small intestinal biospy.
4. Breath test.

How will you define lactase enzyme deficiency?

1. Lactose is a disaccharide and is mainly found in dairy products. Lactose needs a lactase enzyme for its digestion. Lactose intolerance develops when the lactase enzyme is deficient; lactose will not break into glucose and galactose.
2. Lactose intolerance starts in infancy, with S/S of diarrhea, vomiting, and failure to thrive.
3. The patient becomes asymptomatic when lactose is removed from the diet.

What is the epidemiology of Lactase enzyme deficiency?

1. Northern Europeans have normal lactase enzymes, and only 10% to 15% develop lactase enzyme deficiency (Lactose intolerance).
2. The highest incidence is seen in the Asian population like Chines and Japan.
3. Native American >90% show lactase enzyme deficiency (Lactose intolerance).
4. Jews, African Americans, South Americans, and Eastern Europeans have a lesser deficiency, but still, it is seen in 60% to 70%.

How will you discuss the Pathophysiology of lactase enzyme deficiency?

1. Lactose is a disaccharide and is mainly found in dairy products. Lactose needs a lactase enzyme for its digestion. Lactose intolerance develops when the lactase enzyme is deficient; lactose will not break into glucose and galactose.
2. Lactose is a disaccharide and is mainly found in dairy products.
3. Lactose needs a lactase enzyme for digestion. When the lactase enzyme is deficient, lactose will not break into glucose and galactose, causing lactose intolerance.
4. Lactose intolerance starts in infancy, with diarrhea and vomiting. There is failure to thrive.
5. The patient becomes asymptomatic when lactose is removed from the diet.

What is the mechanism of lactase enzyme deficiency?

1. Lactose sugar is present in:
   1. Milk and milk products.
   2. Ice cream.
   3. Yogurt.
   4. Many types of cheese.
2. In case of a lactase enzyme deficiency, lactose can not break into glucose and galactose.
3. The brush borders of the small intestine have the enzyme lactase.
4. When there is a genetic abnormality of lactase enzyme deficiency, milk sugar can not break into monosaccharides.

Lactase enzyme deficiency mechanism

What are the types of Lactase enzyme deficiency?

1. Primary, Congenital:
2. It is the genetic deficiency of the lactase enzyme.
   1. Lactase enzymes appear between 26 to 34 weeks of gestation has 1/3 activity compared to full-term babies.
      1. At 35 to 38 weeks of gestation is around 70%.
      2. Full activity is seen at the 40th week of gestation.
      3. This deficiency appears at the age of 3 to 5 years.
   2. This appears in the newborn.

1. 1. These babies will present with vomiting, diarrhea, malabsorption, and failure to thrive.
   2. This may be seen in premature babies.
2. Secondary (acquired):
3. The  lactase enzyme deficiency is due to:
   1. Gluten sensitivity enteropathy.
   2. Enteritis.
   3. Bacterial growth in the intestine.
   4. Inflammatory bowel disease like Crohn’s disease.
   5. Giardia lambelia infestation.
   6. Cystic fibrosis of the pancreas.
4. Other causes of lactase enzyme deficiency:
5. There is some degree of lactase enzyme deficiency in adults, but severe deficiency occurs due to the following:
   1. Inflammatory bowel disease.
   2. Short-gut syndrome.
   3. Malabsorption syndrome.
   4. Severe acute gastroenteritis.
   5. Prolonged protein-calorie malnutrition.
   6. Certain antibiotics like neomycin and kanamycin.
6. The small bowel is loaded with lactose when lactose is in the intestine.
7. Intestinal bacteria lead to its fermentation and give rise to:
   1. Gas formation.
   2. The osmotic gradient leads to osmotic diarrhea.

Lactase enzyme deficiency

What are the clinical features of Lactase enzyme deficiency?

1. There is abdominal floating.
2. Abdominal cramping.
3. There is flatus.
4. Diarrhea.
5. There is bloating.
   1. These symptoms are worse after the meal.
6. Lactase deficiency in full-term babies or young children is rare.
7. These patients do not thrive.

What are the normal values of Lactase enzyme deficiency?

1. Normal = Glocuse change from the normal value = >30 mg/dL (>1.7 mmol/L).
   1. Inconclusive = 20 to 30 mg/dL
   2. Abnormal = <20 mg/dL  (<1.1 mmpl/L) (positive for lactase enzyme deficiency).
2. Breath test (H⁺) = <10 ppm increase from the baseline is abnormal.

How will you diagnose Lactase enzyme deficiency?

Screening tests for lactase deficiency are:

1. Stool for pH.
   1. Normal stool pH is 7.0 to 8.0
   2. A stool below a pH of 6.0 suggests lactase deficiency.
2. Stool sugar at a time when the patient is symptomatic.
   1. Check for the reducing sugars or glucose by oxidase method.
   2. The presence of glucose in the stool suggests lactase enzyme deficiency.

Lactose tolerance test principle:

1. The principle is like the glucose tolerance test.
2. The patient is provided with lactose overload.
3. Serum glucose levels are estimated by fasting (before lactose administration) and after administration at 15, 30, 60, and 90 minutes.
4. Normal lactase enzyme activity results in postdose glucose elevation of >20 mg/dL (1.1 mmol/L).
5. Lactose will not break into glucose and galactose in the lactase enzyme deficiency; plasma glucose levels will not increase in the blood.
6. This test is a GTT (glucose tolerance test) to detect intestinal disaccharidase (lactase) enzyme deficiency.
   1. Glucose fasting level is compared with other glucose levels to increase or decrease.
7. What are the precautions for a lactose tolerance test?
   1. Avoid strenuous exercise.
   2. Smoking can increase blood glucose levels.
      1. Don’t allow smoking during the test and 8 hours before the test.
   3. Enterogenous steatorrhea. Patients with diabetes mellitus may have increased 20 mg/dL despite the lactase enzyme deficiency.
   4. The patient must fast 8 to 12 hours before the test.
   5. The patient should not eat dark bread, beans, sugars, or high-fiber food within 24 hours of the test.
   6. Don’t allow gum chewing.
   7. Don’t allow antibiotic therapy 2 weeks before the test.
8. Procedure for lactose tolerance test:
   1. After an overnight fast.
   2. Give 50 grams of lactose mixed with 200 mL of water. (1 to 2 grams lactose/kg of body weight).
      1. You can give this with flavored fluid or soft drinks.
   3. Draw the blood sample at 0 (fasting), 30, 60, and 90 minutes intervals. (Some labs check fasting glucose at 30, 60, 90, and 120 minutes).
   4. Some labs check galactose instead of glucose levels.
9. Interpretations:
   1. There is flat lactose tolerance, meaning no glucose level rises.
   2. At normal lactase enzyme level, glucose elevation is >20 mg/dL (1.1 mmol/L) over baseline.
   3. Lactose in the urine produces a positive test for reducing sugars but is negative by the glucose oxidase method.
   4. Take a single blood sample 40 minutes after the test and check the galactose level.

Hydrogen breath test:

1. It is considered the most accurate of the tolerance tests.
2. It is based on the expiratory hydrogen in the breath.
3. Oral Lactose is given to the patient, and the hydrogen in the breath is retested at 30, 60, and 2 to 4 hour intervals.
4. Lactose deficiency results in the deposition of excess lactose in the colon, where bacterial fermentation produces excess hydrogen, which is excreted through the lungs in a breath.

Small intestinal biopsy:

1. It can be done by endoscopy to evaluate the contents of lactose enzyme in the tissue.
2. Tissue biopsy has added advantages to differentiate the sprue.

Summarise the diagnostic tests for lactase enzyme deficiency are?

1. Lactose intolerance test.
2. Hydrogen breath test.
3. Small intestinal biopsy with tissue assay of lactase enzyme.

Questions and answers: