Diagnostic value of zinc protoporphyrin in a screening strategy for alpha-thalassemia.

The definitive diagnosis of alpha-thalassemia involves detection of a deletion of one or more alpha-globin that encode the alpha-chains of Hb (hemoglobin). To determine whether DNA analysis is indicated, screening tests such as mean corpuscular volume (MCV) and Hb typing are employed. alpha-Thalassemia often correlates with normal or low HbA2 values. Zinc protoporphyrin (ZPP) is usually high in ferropenic anemia or lead-poisoning and is normal or slightly raised in beta-thalassemia. Therefore, ZPP is currently used as a marker to discriminate between ferropenic anemia and beta-thalassemia. We investigated the diagnostic potential of ZPP < 150 micromol/mol heme in a screening strategy for alpha-thalassemia. We measured ZPP and performed DNA analysis for detecting the seven most prevalent alpha-thalassemia deletions, namely, alpha3.7, SEA, alpha20.5, alpha4.2, MED, FIL, and THAI, in the blood samples of 200 patients with MCV < 70 fL and HbA2 < or = 3.5%. Deletions were detected in 9% subjects in the ZPP > or = 150 group (n = 175) and 56% subjects in the ZPP < 150 group (n = 29); this difference was statistically significant (chi-square test, P < 0.001). We conclude that ZPP < 150 micromol/mol heme can be used in a new screening strategy for alpha-thalassemia.

Laboratory evaluation of a novel capillary blood sampling device for measuring eight clinical chemistry parameters and HbA1c.

BACKGROUND: The Demecal set enables medically unskilled persons to produce diluted plasma from a single drop of capillary blood at any time and place. The sample is mailed to a certified laboratory for analysis. A marker compound in the dilution buffer enables to correct for individual blood sampling variation. A test dependent factor corrects for recovery of analytes. METHODS: Glucose, cholesterol, triglycerides, HDL and LDL cholesterol, creatinine, BUN, uric acid and HbA1c were evaluated. We studied the correction procedure for sampling variation by the marker compound, the precision of the analyzer in the low range, the influence of characteristics of the set on analyte recovery, and the stability of the samples at different temperatures. RESULTS: Using the marker compound in the buffer, variation in sampling could be corrected accurately. For dilutions up to 15 times, the precision of the analyzer was sufficient. Application of test specific recovery factors gave a good correlation with results of venous blood samples. Samples were stable for 4 days at 4 degrees C, 2-3 days at room temperature and 1 day at 37 degrees C. CONCLUSIONS: The Demecal set can be considered an alternative for venous blood sampling for the tested parameters, enabling patient friendly management of chronic disease.