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Medicina Universitaria

2007, Number 34

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Med Univer 2007; 9 (34)

Factors which affect some neonatal creening tests

Cedillo CB, Estrada GRA, Jonguitud DV, Parra OI

Language: Spanish
References: 18
Page: 3-6
PDF size: 136.33 Kb.


ABSTRACT

Introduction: Analytical laboratory methods used for neonatal screening for inborn errors of metabolism collected from dried blood spot samples on filter paper, are frequently affected by external factors which end up showing confusing results.
Objectives: To establish the factors which have an effect on the neonatal screening tests and their quality control.
Methods: A retrospective and observational analysis of the results from neonatal screening tests performed from June-2002 to October- 2004 was done. The aim of the study was to identify the external factors that were capable to alter the results and to determine which tests are most susceptible. The quality of the dried blood spot sample and the storage and transportation conditions were evaluated as well.
Results: A total of 632 test results were analyzed; in 42 of them (6.6%) abnormal results of either one or several tests were obtained, but in only 11 cases (1.7% of all tests and 26% of those yielding an abnormal initial result) a metabolic disease was indeed present, while in the remaining 31 cases the abnormality of the test resulted from external interference. The most susceptible tests were: glucose-6-phosphate dehydrogenase in 13, galactose uridyl transferase in 9 and immunoreactive trypsinogen in 5. The most common sources of interference were inadequate sample storage and drug administration to the patients, mainly anticonvulsants (valproic acid).
Discussion: When neonatal screening tests are not done with care, the diagnosis of patients with inborn errors of metabolism is delayed. Also, unnecessary retesting is done, which increases the cost. So, the number of rejected samples due to bad quality (clinical or pharmacological interference) should be kept to a minimum.


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