Serum Total Protein and Visceral Protein Status

Visceral Protein Status

• Serum total protein is used as an index for protein status, but it's not a sensitive index as it's maintained within a normal range until significant depletion occurs, and it has a half-life of 14-20 days.
• Serum albumin is a classical test for assessing protein status, but it's not very sensitive for short-term changes, and it has a half-life of 3 weeks.
• Albumin is synthesized in the liver, maintains colloidal oncotic pressure, and functions as a transport protein.
• Albumin levels are affected by confounding factors such as gastrointestinal disorders, renal diseases, liver failure, age, semi-starvation state, and dehydration.

Kwashiorkor and Marasmus

• Kwashiorkor is characterized by low albumin levels and is used to define children susceptible to edema.
• Marasmus is characterized by a low weight for age, but no change in albumin levels is present.

Serum Transferrin

• Serum transferrin is synthesized exclusively in the liver, serves as an iron transport protein, and is located almost intravascularly.
• It has a half-life of 8-10 days, is a negative acute-phase respondent, and is affected by iron status and PEM status.
• The response to dietary treatment is poor, so it cannot be used to monitor protein status in intervention studies.
• Transferrin levels are affected by variables such as renal, liver, and gastrointestinal tract diseases, iron overload, chronic infections, and pregnancy.

Transthyretin (Pre-Albumin)

• Transthyretin is a transport protein for thyroxine and the carrier for retinol-binding protein.
• It has a half-life of 2-3 days, is a negative acute-phase reactant, and is more sensitive than serum albumin and transferrin in monitoring improvements in protein-energy status.
• Transthyretin levels are affected by confounding factors such as gastrointestinal diseases, renal diseases, trauma, stress, infections, and zinc deficiency.

Retinol-Binding Protein

• Retinol-binding protein is a carrier protein for retinol.
• It has a half-life of 12 hours, is a negative acute-phase protein, and is sensitive to protein status but less sensitive to energy status.
• It responds rapidly to dietary treatment, but is unreliable when vitamin A status is compromised.
• Elevated levels are seen in the presence of renal failure, liver diseases, and zinc deficiency, regardless of PEM status.

Somatic Protein Status

• Creatinine is formed in muscles, has a direct correlation with muscle mass, and is an indicator for kidney function and muscle mass.
• The creatinine-height index (CHI) is the urinary excretion of creatinine relative to muscle mass.
• A goal of > 80% of the standard is desirable, with 60-80% indicating mild skeletal depletion, 40-59% indicating moderate skeletal depletion, and < 40% indicating severe skeletal depletion.

Adequacy of Protein Delivery

• Nitrogen balance is the oldest biochemical technique for protein status assessment.
• It is based on the fact that 16% of protein is nitrogen, and nitrogen intake is compared to nitrogen output, adjusted for insensible losses.

Assessment of Nutritional Anemia

• Nutritional anemia can be assessed based on cell size (macrocytic, normocytic, microcytic) and hemoglobin content (hypochromic, normochromic).
• Forms of iron in the body include transferrin, hemoglobin, and storage iron (ferritin).
• Stages of iron deficiency include iron depletion, iron deficient erythropoiesis, and iron deficiency anemia.
• Hemoglobin (Hb) is the most widely used test for iron deficiency anemia, but it's not a good indicator for early iron deficiency and can be affected by factors such as time of day and iron status.
• Hematocrit represents packed cell volume (PCV) and is easy to perform, but it's not sensitive for early iron deficiency and is affected by factors that influence Hb.
• Mean Cell Volume (MCV) is a specific index for iron deficiency anemia, and low MCV is seen in iron deficiency anemia.
• Mean Cell Hemoglobin (MCH) and Mean Cell Hemoglobin Concentration (MCHC) are also used to assess iron deficiency anemia, but MCHC is the least useful as it's the last to fall in iron deficiency anemia.
• Microcytic anemia can be caused by deficiencies in iron, protein, vitamin A, pyridoxine, copper, and manganese, while megaloblastic anemia is related to folate and/or vitamin B12 deficiency.
• Classification of anemia by Complete Blood Count (CBC) can be done using MCV, which is decreased in iron deficiency anemia and increased in folate and B12 deficiency.