Degmacyte

Degmacyte

Background Information of Degmacyte 

A degmacyte (aka "bite cell") is an abnormally shaped RBC with one or more semicircular portions removed from the cell margin.These "bites" result from the removal of denatured hemoglobin by macrophages in the spleen. 

The "bites" in degmacytes are smaller than the missing red blood cell fragments seen in schistocytes.

Clinical Significance

Individuals with RBC enzymopathies involving the pentose phosphate shunt most notably the Glucose-6-phosphate dehydrogenase deficiency, where the uncontrolled oxidative stress causes hemoglobin to denature and precipitate to form inclusions called Heinz bodies.

Additionally, they can also be seen in drug-induced hemolysis. These drugs may have  constituents or metabolites that contain amino, nitro or hydroxy groups.

Cellular Description

The hallmark of the Degmacyte is the presence of one or a few small semicircular portions of the RBC cell surface "biten" off.

Glucose-6-Phosphate Dehydrogenase Qualitative Screening

Glucose-6-Phosphate Dehydrogenase (G6PDH) Qualitative Screening

BackGround Information

G-6-PDH deficiency in RBCs have been demonstrated to be the basis for certain drug-induced
haemolytic anaemias. Hence, Severe haemolytic anaemia may result in these individuals when they are given many commonly used drugs.This emphasized the importance of identifying individuals with this biochemical defect as an aid in the selection of therapeutic agents.  The majority of
patients who have demonstrated G-6-PDH deficiency are clinically normal until exposed to one of
several oxidant drugs (anti-malarial drugs, sulfa drugs, ascorbic acid and others).

This defect should be considered whenever an otherwise unexplained case of haemolytic anaemia is
encountered.

Red cell G-6-PDH deficiency has been found in about 13% of African-American males and in
about 3% of African-American females. The incidence is also high among other racial and ethnic
groups, such as Sardinians, Greeks and Sephardic Jews.

Principle of Fluorescence-Based Test Kit

For semi-quantitative purposes, the highly suggested method is to estimate G6PDH in terms of visual appearance of fluorescence in red cell substrate mixtures. Many diagnostic kits in the commercial market involves the reaction:

Method

1. Whole blood is usually collected with EDTA, heparin or acidcitratedextrose.
2. Incubate a small amount of blood with glucose-6-phosphate and nicotinamide adenine dinucleotide phosphate (NADP). 
3. Drops of the mixture are removed at 5-minute intervals, spotted on filter paper 
4. Viewed under long-wave ultraviolet light in a viewing box or a darkened room

* Fluorescence is clearly evident in mixtures prepared from normal blood, whereas deficient
samples yield little or no fluorescence.

Expected Results

• Normal sample: demonstrate moderate to strong fluorescence after 5 minutes, and strong fluorescence after 10 minutes.
• Intermediate level sample: demonstrate weak fluorescence after 5 minutes and
• Moderate level sample: fluorescence after 10 minutes.
• Deficient Level Sample: very faint or no fluorescence even after 10 minutes

Heinz Bodies

Heinz Bodies

Background Information of Heinz Bodies

Heinz bodies (also referred to as "Heinz-Ehrlich bodies") are inclusions within RBCs composed of denatured hemoglobin.

Clinical Significance

Heinz bodies are formed by damage to the hemoglobin component molecules, usually through oxidant damage, or from an inherited mutation (i.e. change of an internal amino acid residue). 

As a result, an electron from the hemoglobin is transferred to an oxygen molecule, which creates a reactive oxygen species (ROS) that can cause severe cell damage leading to premature cell lysis. Damaged cells are cleared by macrophages in the spleen, where the precipitate and damaged membrane are removed, leading to characteristic "bite cells". The denaturing process is irreversible and the continual elimination of damaged cells leads to Heinz body anemia.

There are several pathways leading to the hemoglobin damage.

• NADPH deficiency can cause a dysfunction in glutathione peroxidase which is an enzyme that converts hydrogen peroxide(ROS) into water.
• G6PD (glucose-6-phosphate dehydrogenase) deficiency exacerbated by administration of oxidant drugs (e.g., primaquine, dapsone, quinidine) can also result in Heinz bodies. G6PD deficient red cells in combination with high levels of oxidants causes a cross-linking of sulfhydryl groups on globin chains which causes a denaturing and formation of Heinz body precipitates.

• Chronic liver disease
• Alpha-thalassemia:  Patients whom have partial or complete defects in alpha globin production, leading to a relative abundance of beta globin chains in the cell. These excess beta globin chains aggregate to form HbH, which has decreased solubility and precipitates in the RBC cytoplasm. This is not direct damage to hemoglobin per se, but rather a perturbation in the quaternary structure of hemoglobin.
• Hyposplenism/asplenia: damaged or absent spleen cannot remove these damaged cells from circulation.

Cellular Description

Heinz bodies appear as small round inclusions within the red cell body, though they are not visible when stained with Romanowsky dyes. They appear more clearly when supravitally stained (e.g., with new methylene blue or bromocresol green).

WBC Correction for the Presence of Nucleated Red Blood Cells

WBC Correction for the Presence of Nucleated Red Blood Cells (nRBCs) 

Due to the fact that nRBCs present in the whole blood are not lysed by the diluting fluid when a WBC count is performed and the fact that most automated analyzers will miscount them as small round lymphocytes, a WBC correction needs to be performed. 

In most of the cases, when an instrument/automated analyser "flagged" for nRBCs seen/observed/suspected, a thin blood smear will be performed for manual microscopy. If there are more than 5 nRBCs seen per 100 WBC’s after performing a differential count, the total white count MUST be corrected for the presence of these nucleated red cells.  The formula is as follows:

     Uncorrected WBC count   X   100               =    corrected WBC count (mm³⁾

number of nRBC’s per 100 WBC’s + 100

The count should be reported as a corrected WBC count..

Example:  8 nucleated red blood cells are seen while performing a differential on a smear of peripheral blood from a patient.  The WBC count reported by the Coulter Counter was 17,400 mm³.  Hence to calculate the actual leukocyte count, the above formula will be activated

                        17,400  X  100    =    1740000    =   16,111 mm³  corrected

                             8 + 100                     108