Neonatal screening for severe combined immunodeficiency caused by an adenosine deaminase defect: A reliable and inexpensive method using tandem mass spectrometry

Abstract

Background: Adenosine deaminase (ADA)-severe combined immunodeficiency (SCID) is an SCID caused by a defect in the enzyme adenosine deaminase. It is usually fatal in infancy because of severe recurrent infections. When diagnosis is made, permanent damage caused by infections or by metabolites is often present. Gene therapy, bone marrow transplantation, or enzyme therapy might be effective if performed early. ADA-SCID complies with all the criteria for inclusion in a newborn screening program. However, screening methods are still expensive or provide a non-negligible number of indeterminate results. Objective: The aim of the present study was to develop a simple, reliable, and inexpensive method for diagnosis of ADA-SCID by using dried blood spot (DBS) samples taken at birth. Cost per test was calculated, including the cost for reagents, equipment, and operators. Methods: DBS samples from 4 patients with genetically confirmed ADA-SCID and 12,020 DBS samples from healthy newborns were examined. Adenosine and 29-deoxyadenosine were tested by using tandem mass spectrometry (PCT EP2010/ 070517). Results: The mean levels of adenosine and 29-deoxyadenosine were 7.8 6 3.1 and 8.5 6 6.0 mmol/L, respectively, in affected children; adenosine was found at 0.23 6 0.09 mmol/L, whereas 29-deoxyadenosine was never detected in healthy control subjects (adenosine: P < 10 26 [95% confidence limit, 7.59-7.78] and 29-deoxyadenosine: P < 10 26 [95% confidence limit, 8.65-8.82] for control subjects vs patients with ADA-SCID). No indeterminate or false-positive results were found. Cost per test was V0.01 ($0.013). A pilot population-based newborn screening for ADA-SCID has started in Tuscany, Italy. Conclusion: Tandem mass spectrometry can be used for diagnosis of one of the most frequent form of SCID at a negligible cost. (J Allergy Clin Immunol 2011;127:1394-9.)

Tandem mass spectrometry, but not T-cell receptor excision circle analysis, identifies newborns with late-onset adenosine deaminase deficiency

“…The mean adenosine and 29-deoxyadenosine levels in patients P1 to P3 were 12.0-and 27.6-fold higher, respectively, than the mean normal values obtained in 50,000 non-ADA-deficient newborns. 29-Deoxyadenosine levels in patients P1 to P3 and patient P4 were lower than those previously reported by our group for 3 different patients with early-onset ADA-SCID (P5-P7; 2.5, 5.3, and 16.2 mmol/L), 12 although the difference in levels was not statistically significant. On the other hand, adenosine levels were greater in patients P1 to P3 compared with those seen in patients with early-onset disease (P5-P7), without reaching statistical significance (Table I).…”

“…Analysis of ADA metabolites by means of tandem-MS would have a low cost 12 in most laboratories that already screen newborns by using tandem-MS. Actually, laboratories that perform tandem-MS with hydrazine could be able to also analyze adenosine and 29-deoxyadenosine at no extra cost. The method could also be used, at no extra cost, in laboratories that substitute water for hydrazine.…”

“…However, we recommend the inclusion of tandem-MS analysis of adenosine and 29-deoxyadenosine, which is inexpensive 12 and can identify newborns with severe and hypomorphic variants of ADA, who might have SCID later in life. Moreover, tandem-MS can be useful in countries that cannot afford TREC analysis but are already using tandem-MS to screen for other metabolic diseases.…”

“…The method for identifying ADA metabolites in DBSs has been patented (PCT EP2010/070517) and validated by using 12,000 DBSs from healthy newborns. 12 Normal values of adenosine are less than 1.5 mmol/L, and 29-deoxyadenosine is not detectable in DBSs collected at birth from newborns without ADA deficiency. The method produced no false-positive results in 50,000 screened newborns, with no difference between full-term or premature births.…”

“…10,11 We have recently shown that it is possible to identify patients with ADA-SCID using tandem mass spectrometry (tandem-MS) on DBSs collected at birth during routine newborn screening procedures at a low cost (0.01V per test). 12 An expanded newborn screening including more than 40 metabolic diseases is now performed by using tandem-MS in many countries in the world, so that millions of children worldwide are screened each year for those diseases. 13 In the Tuscany region of Italy, ADA-SCID has been added to the panel of diseases for which tandem-MS screens.…”