Reliability of quantitative and qualitative tests to identify heterozygotes carrying severe or mild G6PD deficiency.

OBJECTIVES: To determine if the qualitative test (cytochemical) is more reliable than the quantitative test (differential pH-metry) in identifying heterozygous G6PD- subjects. DESIGN AND METHODS: Identification of heterozygous G6PD- subjects was done by the measurement of G6PD activity and by a cytochemical test. RESULTS: A cytochemical test is more sensitive than differential pH-metry to identify heterozygous G6PD- subjects. CONCLUSIONS: A cytochemical test is a reliable method for mass screening for G6PD deficiency to identify G6PD- heterozygotes.

G6PD/PK ratio: a reliable parameter to identify glucose-6-phosphate dehydrogenase deficiency associated with microcytic anemia in heterozygous subjects.

OBJECTIVES: To determine if measuring the ratio of glucose-6-phosphate dehydrogenase (G6PD) to pyruvate kinase (PK) is more reliable than only measuring G6PD activity to identify heterozygous G6PD- individuals with associated microcytic anemia in the Calabrian population, which shows high frequencies of both the thalassaemia (thal) trait and G6PD deficiency. DESIGN AND METHODS: Measurement of G6PD and PK activities was carried out on 205 samples of whole blood from Calabrian subjects of both sexes (age range 10-50 years) using a double starter differential pH-metry technique. RESULTS: The G6PD/PK ratio is able to differentiate G6PD- heterozygous individuals from the normal population. G6PD/PK values also allowed us to easily identify the G6PD- heterozygous subjects with microcytic anaemia. Student's t test shows that G6PD/PK ratio is more reliable in both sample groups, relative to G6PD activity in normal subjects. CONCLUSIONS: G6PD/PK ratio is a reliable diagnostic parameter for mass screening for G6PD deficiency.

Body weight influences pharmacokinetics of levodopa in Parkinson's disease.

Changes in body weight may induce substantial variations in peripheral pharmacokinetics of drugs, but the relation between body weight and levodopa (LD) pharmacokinetics has never been investigated in Parkinson's disease. To address this issue, we conducted a pharmacokinetic study with 164 patients with sporadic Parkinson's disease. Patients underwent an oral acute LD test with 250 mg of LD, and pharmacokinetic variables were assessed at baseline and at 30, 60, 120, and 240 minutes after LD administration. Plasmatic-LD areas under the curve and body weight were significantly and inversely correlated as well as the elimination of the half-life of LD and body weight. In our sample, women were significantly lighter and had a significantly greater area under the curve than men. Moreover, a greater percentage of women showed LD peak-dose dyskinesias compared with men. Our findings suggest that lighter patients with Parkinson's disease probably receive a greater cumulative dosage of LD per kilogram of body weight during long-term treatment, because in clinical practice, LD is administered without any adjustment of the dose to body weight. This could explain gender differences for the development of LD-induced peak-dose dyskinesias observed during the course of the disease.