Application value of Glucose-6-Phosphate Dehydrogenase Assay Kit (Substrate Method) in clinical screening

Clinical Background and Testing Needs of G6PD Deficiency

Glucose-6-phosphate dehydrogenase (G6PD) is a key enzyme in the pentose phosphate pathway within red blood cells. A decrease in its activity can lead to reduced production of reduced coenzyme II, thereby weakening the red blood cells' ability to withstand oxidative stress damage. Clinically, G6PD deficiency is a common X-linked incompletely dominant inherited disorder and holds an important position in newborn screening and premarital examinations in certain high-prevalence regions. Quantitative activity testing using a glucose-6-phosphate dehydrogenase assay kit (glucose-6-phosphate substrate method) can provide clinicians with an objective reference for enzyme activity and assist in determining whether there is a risk of deficiency.

Kit Detection Principle and Method Characteristics

This kit employs the glucose-6-phosphate substrate method. The basic reaction principle is as follows: at 37°C, G6PD in the sample catalyzes the reaction between the substrate glucose-6-phosphate and the coenzyme NADP⁺ to generate 6-phosphogluconolactone and NADPH. NADPH has a characteristic absorption peak at 340 nm. By monitoring the rate of change in absorbance per unit time, enzyme activity can be calculated. Compared with the ultraviolet rate method, the substrate method reagent formulation typically contains stabilizers and substrate protectants, which under common specifications can reduce the influence of endogenous interfering substances (such as glutathione reductase). This method generally requires fresh whole blood or washed red blood cell lysate as the sample. Before measurement, attention should be paid to the choice of anticoagulant (commonly heparin or EDTA) and sample storage conditions (stability at 2–8°C generally does not exceed 24 hours).

Clinical Application Scenarios and Key Points for Result Interpretation

In newborn screening for inherited metabolic disorders, G6PD activity measurement is one of the routine items. Quantitative testing using a glucose-6-phosphate dehydrogenase assay kit (glucose-6-phosphate substrate method) can distinguish three grades: normal, intermediate deficiency, and severe deficiency. It should be noted that in female heterozygotes, due to random X-chromosome inactivation, enzyme activity may fall within the normal range or at borderline values; in such cases, judgment should be made comprehensively in combination with genetic testing or family history. In the differential diagnosis of anemia in adults, if acute hemolytic episodes occur and autoimmune hemolysis has been excluded, the possibility of G6PD deficiency should be considered. In addition, certain drugs (such as sulfonamides, antipyretic-analgesic drugs, vitamin K and its derivatives) may induce hemolysis, and testing G6PD activity before medication can help with risk assessment. For clinical interpretation, the reference intervals provided in the kit instructions should be consulted, and different laboratories need to establish or verify their own reference ranges.

Quality Control and Precautions

To ensure reliable test results, matching quality control materials should be used for each measurement. For kits of common specifications, it is recommended to run high- and low-value quality controls daily. During operation, if hemolysis interference is severe, resampling is required, because enzymes released from disrupted red blood cells may falsely elevate activity. In addition, leukocytes and platelets in the sample also express G6PD, but at relatively low levels, generally not affecting the overall result. The kit storage conditions (usually 2–8°C, protected from light) and open-bottle stability must be strictly followed. Laboratories should evaluate inter-batch precision based on routine testing volume to ensure long-term comparability of results. Overall, as a screening tool, this kit can provide valuable clinical reference but cannot be used alone as a basis for definitive diagnosis; when necessary, follow-up testing should be combined.