G6PD


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Related to G6PD: G6PD deficiency

G6PD

glucose-6-phosphate dehydrogenase.

glucose-6-phosphate dehydrogenase (G6PD) deficiency

an inherited disorder characterized by red cells partially or completely deficient in G6PD, an enzyme critical in aerobic glycolysis. A sex-linked disorder, the defect is fully expressed in affected males despite a heterozygous pattern of inheritance. The disorder is associated with episodes of acute hemolysis under conditions of stress or in response to certain chemicals or drugs, particularly quinine. The anemia that results is a nonspherocytic hemolytic anemia. See also congenital nonspherocytic hemolytic anemia, favism.
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Glucose-6-phosphate dehydrogenase

glucose-6-phosphate dehydrogenase (G6PD) test

a blood test to diagnose G6PD deficiency in suspected individuals. Deficiency of this enzyme causes precipitation of hemoglobin and cellular membrane changes, possibly resulting in hemolysis of variable severity, a sex-linked trait carried on the X chromosome.

Glucose-6-Phosphate Dehydrogenase

Synonym/acronym: G6PD.

Common use

To identify an enzyme deficiency that can result in hemolytic anemia.

Specimen

Whole blood (1 mL) collected in a lavender-top (EDTA) tube.

Normal findings

(Method: Fluorescent) Qualitative assay—enzyme activity detected; quantitative assay—the following table reflects enzyme activity in units per gram of hemoglobin:
AgeConventional UnitsSI Units (Conventional Units × 0.0645)
Newborn7.8–14.4 international units/g hemoglobin0.5–0.93 micro units/mol hemoglobin
Adult–older adult5.5–9.3 international units/g hemoglobin0.35–0.60 micro units/mol hemoglobin

Description

Glucose-6-phosphate dehydrogenase (G6PD) is a red blood cell (RBC) enzyme. It is involved in the hexose monophosphate shunt, and its function is to protect hemoglobin from oxidation. G6PD deficiency is an inherited X-linked abnormality; approximately 20% of female carriers are heterozygous. This deficiency results in hemolysis of varying degrees and acuity depending on the severity of the abnormality. There are three G6PD variants of high frequency in different ethnic groups. G6PD A–is more common in African Americans (10% of males) than in other populations. G6PD Mediterranean is especially common in Iraqis, Kurds, Sephardic Jews, and Lebanese and less common in Greeks, Italians, Turks, North Africans, Spaniards, Portuguese, and Ashkenazi Jews. G6PD Mahidol is common in Southeast Asians (22% of males). Polymerase chain reaction (PCR) methods that can detect gene mutations for the enzyme in whole blood are also available. Counseling and written, informed consent are recommended and sometimes required before genetic testing.

This procedure is contraindicated for

    N/A

Indications

  • Assist in identifying the cause of hemolytic anemia resulting from drug sensitivity, metabolic disorder, or infection
  • Assist in identifying the cause of hemolytic anemia resulting from enzyme deficiency

Potential diagnosis

Increased in

  • The pathophysiology is not well understood but release of the enzymes from hemolyzed cells increases blood levels.

  • Chronic blood loss (related to reticulocytosis; replacement of RBCs)
  • Hepatic coma (pathophysiology is unclear)
  • Hyperthyroidism (possible response to increased basal metabolic rate and role of G6PD in glucose metabolism)
  • Idiopathic thrombocytopenic purpura
  • Megaloblastic anemia (related to reticulocytosis; replacement of RBCs)
  • Myocardial infarction (medications [e.g., salicylates] may aggravate or stimulate a hemolytic crisis in G6PD-deficient patients)
  • Pernicious anemia (related to reticulocytosis; replacement of RBCs)
  • Viral hepatitis (pathophysiology is unclear)

Decreased in

    Congenital nonspherocytic anemia G6PD deficiency Nonimmunological hemolytic disease of the newborn

Critical findings

    N/A

Interfering factors

  • Drugs that may increase G6PD levels include fluorouracil.
  • Drugs that may precipitate hemolysis in G6PD deficient individuals include acetanilid, acetylsalicylic acid, ascorbic acid, chloramphenicol (Chloromycetin), dapsone, doxorubicin, furazolidone, isobutyl nitrate, methylene blue, nalidixic acid, naphthalene, niridazole, nitrofurantoin, para-aminosalicylic acid, pentaquine, phenacetin, phenazopyridine, phenylhydrazine, primaquine, quinidine, quinine, sulfacetamide, sulfamethoxazole, sulfanilamide, sulfapyridine, sulfisoxazole, thiazolsulfone, toluidine blue, trinitrotoluene, urate oxidase, and vitamin K.
  • G6PD levels are increased in reticulocytes; the test results may be falsely positive when a patient is in a period of acute hemolysis. G6PD levels can also be affected by the presence of large numbers of platelets and white blood cells, which also contain significant amounts of the enzyme.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching:   Inform the patient this test can assist in diagnosing anemia.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s hematopoietic system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues,  as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Nutritional Considerations: Educate the patient with G6PD deficiency, as appropriate, to avoid certain foods, vitamins, and drugs that may precipitate an acute episode of intravascular hemolysis, including fava beans, ascorbic acid (large doses), acetanilid, antimalarials, furazolidone, isobutyl nitrate, methylene blue, nalidixic acid, naphthalene, niridazole, nitrofurantoin, phenazopyridine, phenylhydrazine, primaquine, sulfacetamide, sulfamethoxazole, sulfanilamide, sulfapyridine, thiazolsulfone, toluidine blue, trinitrotoluene, and urate oxidase.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include biopsy bone marrow, bilirubin, CBC, CBC RBC morphology (including examination of peripheral smear for the presence of Heinz bodies), direct antiglobulin test, folate, Ham’s test, haptoglobin, hemosiderin, newborn screening, osmotic fragility, reticulocyte count, UA, and vitamin B12.
  • Refer to the Hematopoietic System table at the end of the book for related tests by body system.

G6PD

glucose-6-phosphate dehydrogenase.
References in periodicals archive ?
Compared to the traditional approach of administering antioxidants that react directly with oxygen, we have stimulated all the cell's natural antioxidant mechanisms by raising G6PD levels, and its by-product, NADPH," emphasizes Mari Carmen GEmez-Cabrera, co-author of the paper and researcher at the University of Valencia.
Conclusion: Frequency of G6PD defffiency is higher in neonatal hyperbilirubinemia.
Glucose-6-phosphate dehydrogenase deficiency and malaria: cytochemical detection of heterozygous G6PD deficiency in women.
Some antibiotics taken by breastfeeding mothers may occasionally be associated with adverse effects in their infants: TMP/SMX may cause poor feeding; amoxicillin and cephalexin may cause diarrhea; nitrofurantoin may cause diarrhea or, in infants with G6PD deficiency, hemolytic anemia; and ciprofloxacin may cause pseudomembranous colitis in infants and green teeth in neonates (SOR: C, case reports and expert opinion).
But G6PD is not a uniquely Filipino disease, and in the Philippines it has higher incidence in areas like the Cordillera because it gives people a certain degree of protection from malaria, a disease which is endemic in that region.
Factors increasing serum bilirubin in newborns Increased destruction * G6PD dysfunction of red blood cells * Untreated rhesus incompatibility * ABO group incompatibility * Genetic blood cell defects * Sepsis * Birth trauma with haematoma formation Decreased plasma * Prematurity albumin concentration * Infection or illness * Competition for binding sites by drugs, eg sulphon amides, salicylates Decreased conjugation * Immature enzyme systems in liver * Genetic disorders * Inhibition by drugs eg amitriptyline, ketoconazole Increased reabsorption * Dehydration from gut * Constipation * Immature gut with poor motility * Breastfeeding
Other causes in their study were G6PD deficiency, hypothyroidism, UTI, septicaemia, Down syndrome & ABO incompatibility.
I would like to add to this well written article that we have also reported acquired methemoglobinemia cases with administration of cytanest in puerperal women with G6PD deficiency and infants in whom erythrocyte cytochrome 65 reductase was assoyed (1-4), which is the main enzyme for methemoglobin reductase in erythrocytes as mentioned by the authors.
For example, in regions in which malaria is of concern, such as Africa, individuals with the mutant recessive form of the G6PD gene are resistant to malaria.
Sickle cell disease and other haemoglobin disorders such as thalassaemia and G6PD are inherited blood diseases that affect how oxygen is carried in the body.
Studies were undertaken to look for the prevalence of anaemia, worm infestation and haemoglobinopathy disorders like sickle cell disease, thalassaemia and G6PD deficiency.
In "Answering your questions" (Tips, November 2010, page 32) regarding G6PD testing, Dr.