Dried Blood Spot Adequate For Vitamin A Deficiency Diagnosis
Vitamin A deficiency (VAD) and anemia are the most prevalent nutritional deficiency in children globally. The dried blood spot (DBS) method has been used in prevalence studies of VAD and anemia in different age groups, but it has not yet been validated for children. However, reports from a recent study show that the dried blood spot (DBS) method is adequate for the diagnosis of Vitamin A deficiency in preschool children, but not for anemia.

Researchers aimed to assess the reproducibility and validity of the dried blood spot technique in the diagnosis of Vitamin A deficiency and anemia in preschoolers. The researchers collected venous and capillary blood samples from a representative sample of children lesser than 5 years old who attended the public health system in Rio de Janeiro. Serum retinol and hemoglobin were measured in 235 and 182 children, respectively.

Serum retinol was measured with HPLC and hemoglobin was measured with spectrophotometry in samples of venous (gold standard) and capillary blood (test method, DBS). DBS reproducibility was assessed with the intraclass correlation coefficient (ICC), and prevalence-adjusted and bias-adjusted (PABAK).

DBS validity was assessed with sensitivity, specificity, accuracy index (AI), positive predictive value (PPV), and negative predictive value (NPV). The study revealed that DBS method showed very good reproducibility for serum retinol and very good/good reproducibility for hemoglobin. Moreover, the prevalence rates for VAD by the reference and test methods were 11.5% and 11.9%, respectively, whereas the anemia rates were 19.2% and 46.2%.

The authors also highlighted that the test method showed low sensitivity (33%) and PPV (32%) and high specificity (91%) and NPV (92%) for serum retinol. For hemoglobin, the test method showed fair sensitivity (71%), low PPV (30%), fair specificity (60%), and high NPV (90%). AI was 83% for VAD and 62% for anemia. As a result, it was concluded that DBS method is considered adequate for the diagnosis of VAD in preschool children, but not for anemia.

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