Glucose-6-phosphate dehydrogenase deficiency neonatal screening: preliminary evidence that a high percentage of partially deficient female neonates are missed during routine screening

Objectives-To provide preliminary evidence that the currently employed semi quantitative method of screening for glucose-6-phosphate dehydrogenase (G6P D) deficiency can only detect infants who are totally deficient for G6PD an d misses all cases of partial G6PD deficiency. Setting-General population: 2150 randomly selected blood samples from the B lood Donation Department, Speliopouleion General Hospital, Athens, Greece. Neonate population: 2000 samples from neonates (50% male; 50% female) in ma ternity hospitals in the greater Athens area. High risk population: a total of 545 individuals from 133 families in the Athens area, the minimum accep tance criteria being the parents and any brother or sister. Method-Blood specimens from neonates or adults were collected and either sp otted and dried on special filter paper (Schleicher and Schull 2992, Darmst adt, Germany) or used in tubes after being heparinised. For the quantitativ e evaluation of G6PD enzyme activity, the Quantase G6PD screening kit (Quan tase Limited, Perth, UK) was used. Quantase G6PD controls (Quantase Limited ) were used at three levels of G6PD. These controls are rated at 24, 30, an d 37 degrees C. Alternatively, we used the Sigma G6PDH controls (Sigma Chem ical Company, St Louis, USA) which are rated at 30 and 37 degrees C. The as say was performed according to the instructions included in the kit with th e modification for haemoglobin normalisation. Results-General population: 36 females who were classified as having normal enzymatic activity with the semiquantitative test, were classified as part ially deficient with the quantitative test. Neonate population: using the q uantitative test, the percentage of G6PD deficient neonates in this populat ion was 5.5%, compared with 3.17% reported in routine screening using the s emiquantitative method. High risk population: the quantitative method detec ted 28 cases of total or partial G6PD deficiency in sisters of males with k nown total deficiency. The semiquantitative method only detected 32% (nine out of 28) of these cases. Conclusions-A considerable amount of partially G6PD deficient female neonat es (heterozygotes) are undetected and classified as having normal enzymatic activity using the semiquantitative method, which uses a cut off of 2.1 U/ g haemoglobin (Hb). The use of a fully quantitative G6PD screening kit is p roposed, employing the automated haemoglobin normalisation and a cut off of 6.4 U/g Hb. Any neonate with an activity below this mark should be regarde d as G6PD deficient, and all preventive measures should be taken.