Newborn screening with tandem mass spectrometry: examining its cost-effectiveness in the Wisconsin Newborn Screening Panel.

OBJECTIVE: To examine the cost-effectiveness of tandem mass spectrometry (MS/MS) in a neonatal screening panel for 14 fatty acid oxidation and organic acidemia disorders in the Wisconsin Newborn Screening Program. STUDY DESIGN: An incremental cost-effectiveness analysis with a hypothetical cohort of 100,000 infants was performed. A threshold of $50,000/QALY (quality-adjusted life-year) was used to determine whether screening for medium-chain acyl-CoA dehydrogenase deficiency (MCAD) alone is cost-effective or whether additional disorders would need to be incorporated into the analysis to arrive at a conclusion regarding the overall cost-effectiveness of MS/MS. RESULTS: Under conservative assumptions, screening for MCAD alone yields an incremental cost-effectiveness ratio of $41,862/QALY. With the use of more realistic assumptions, screening becomes more cost-effective ($6008/QALY) and remains cost-effective so long as the incremental cost of screening remains under $13.05 per test. Adding the incremental costs of detecting the 13 other disorders on the screening panel still yields a result well within accepted norms for cost-effectiveness ($15,252/QALY). CONCLUSIONS: In Wisconsin, MS/MS screening for MCAD alone appears to be cost-effective. Future analyses should examine the cost-effectiveness of alternative follow-up and treatment regimens for MCAD and other panel disorders.

Multiple acyl-CoA-dehydrogenase deficiency (MADD): use of acylcarnitines and fatty acids to monitor the response to dietary treatment.

The treatment of multiple acyl-CoA-dehydrogenase deficiency (MADD) includes a low-fat, low-protein, high-carbohydrate diet, avoiding long fasting periods. However, there is no useful biochemical marker to determine the response to different diets or fasting periods. The aims of this study are to report a patient with MADD, diagnosed through a newborn screening program using tandem mass spectrometry, to assess her response to different feedings, and to evaluate the usefulness of acylcarnitines and FFA to monitor the response to dietary changes. The patient was diagnosed at 6 d. Family history revealed three dead siblings. Five tests were performed, one with breast milk and the subsequent four after giving the patient a bottle of a low-fat, low-protein formula (F), F with glucose polymers (GP), F+GP plus uncooked corn starch (CS), or F+GP+CS preceded by amylase. The results showed that acylcarnitines, FFA, and total nonesterified fatty acids levels were greatly improved at 2 and 4 h on F+GP compared with breast milk. At 6 mo of age, the test with F+CS was repeated to assess the response to a longer fast. The results were similar at 2 and 4 h, but showed a marked increase of acylcarnitines, FFA, and total nonesterified fatty acids at 6 h. The increase of these metabolites could not be avoided by the use of F+GP+CS, but was prevented when amylase was used simultaneously. The patient is currently 3.9 y old and has normal growth and development. We conclude that diagnosis of MADD through a newborn screening program using tandem mass spectrometry is suitable; acylcarnitines and FFA are useful to monitor the response to treatment; and exogenous amylase allows the use of CS in small children with MADD. This therapeutic approach may be an alternative to the use of continuous overnight feedings used for young children with severe fatty acid oxidation defects. Early diagnosis and treatment may change the natural history of MADD.

Clinical and biochemical characterization of short-chain acyl-coenzyme A dehydrogenase deficiency.

OBJECTIVE: We identified two additional patients with short-chain acyl-coenzyme A (CoA), further characterized the clinical and biochemical features of this defect, and compared it with other fatty acid oxidation defects. DESIGN: We have measured the in vitro short-chain acyl-coenzyme A dehydrogenase (SCAD) activity in six affected persons with the electron-transfer flavoprotein-linked assay in the presence and absence of anti-medium-chain acyl-CoA dehydrogenase antibody. Urine organic acids, acylglycines, acylcarnitines, and radiolabeled substrate catabolism by skin fibroblasts were also examined. RESULTS: All patients had some neurologic abnormalities, including hypotonia, hypertonia, or seizures. None of the patients had episodes of hypoglycemia; in the only patient tested, fasting ketogenesis was not impaired. Four patients were initially seen in the neonatal period, two with profound metabolic acidosis and two with mild acidemia; the other two cases were recognized in infancy. Enzymatic analysis of cultured skin fibroblasts demonstrated approximately 10% activity of SCAD when compared with control fibroblasts. Gas chromatography and mass spectrometry of urine revealed that ethylmalonic acid was present in all samples but not always at elevated concentrations; methylsuccinic acid and butyrylglycine were sporadically elevated. n-Butyrylcarnitine was often found in urine and plasma. Radiolabeled substrate metabolism was reduced to 40% to 60% of control values. CONCLUSIONS: Because affected persons do not consistently excrete characteristic metabolites, the diagnosis of this enzymatic deficiency is difficult. It is necessary to collect and analyze several urine and plasma specimens when the diagnosis is being considered in patients with neurologic abnormalities suggestive of this disorder.

When do gut flora in the newborn produce 3-phenylpropionic acid? Implications for early diagnosis of medium-chain acyl-CoA dehydrogenase deficiency.

Urinary excretion of 3-phenylpropionylglycine (PPG) is a diagnostic marker for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. PPG is derived from 3-phenylpropionic acid (PPA), a product of anaerobic bacterial metabolism in the gut. To determine when the infant gut was colonized with PPA-producing bacteria, we cultured stool in prereduced thioglycollate broth from 93 apparently healthy infants. We analyzed the products of bacterial metabolism by gas chromatography/mass spectrometry for the presence of PPA. Trend analysis demonstrated a significant difference (P less than 0.001) in PPA production between early and later infancy. PPA was not detected in 84% of media isolated from stool collected from infants younger than four months. For older infants, 67% of the samples were PPA-positive. Thus, because the normal gut is not sufficiently colonized with PPA-producing bacteria before three to four months of age, PPG analysis alone is not a sensitive marker for the early detection of MCAD deficiency. Using stable isotope dilution mass spectrometry, we measured PPG and n-hexanoylglycine (HG) excretion in two well newborns with MCAD deficiency. HG, believed to be an endogenous metabolite associated with MCAD deficiency, was consistently above normal in all urine samples.

Recognition of medium-chain acyl-CoA dehydrogenase deficiency in asymptomatic siblings of children dying of sudden infant death or Reye-like syndromes.

The medium-chain acyl-CoA dehydrogenase (MCAD) deficiency of mitochondrial beta oxidation has been identified in two asymptomatic siblings in a family in which two previous deaths had been recorded, one attributed to sudden infant death syndrome and the other to Reye syndrome. Recognition of this disorder in one of the deceased and in the surviving siblings was accomplished by detection of a diagnostic metabolite, octanoylcarnitine, using a new mass spectrometric technique. This resulted in early treatment with L-carnitine supplement in the survivors, which should prevent metabolic deterioration. Further studies suggest that breast-feeding may be protective for infants with MCAD deficiency. Families with children who have had Reye syndrome or in which sudden infant death has occurred are at risk for MCAD deficiency. We suggest that survivors and asymptomatic siblings should be tested for this treatable disorder.

Octanoic acidemia and octanoylcarnitine excretion with dicarboxylic aciduria due to defective oxidation of medium-chain fatty acids.

Five patients aged 7 to 21 months are described who developed attacks of coma after a short prodromal illness with diarrhea or vomiting or both. Four had concomitant hypoglycemia, and all had hypoketonemia, with excessive urinary excretion of medium-chain dicarboxylic acids, medium-chain (omega-1)-hydroxyacids, suberylglycine, hexanoylglycine, and octanoylcarnitine. All patients accumulated octanoic acid, decanoic acid, and cis-4-decenoic acid in plasma. Fibroblasts from three patients showed a decreased rate of octanoate oxidation (10%, 12%, and 29% of control values, respectively). These findings suggest a deficiency of medium-chain acyl-CoA dehydrogenase, most probably an autosomal recessive inherited metabolic disorder. Two of the patients died during an acute attack, and a third had severe neurologic sequelae; the two remaining patients recovered. Plasma free carnitine levels were low, but total carnitine was normal. The three surviving patients underwent a fasting test, which did not lead to hypoglycemia, although hypoketonemia, dicarboxylic aciduria, and excessive mobilization of fatty acids did occur. The surviving patients were maintained on frequent carbohydrate-enriched meals.

Medium-chain acyl-CoA dehydrogenase deficiency in two siblings with a Reye-like syndrome.

An increasing number of reports indicate that patients with some inherited metabolic diseases may have symptoms resembling those of Reye syndrome. We describe two siblings who developed a Reye-like syndrome at ages 16 and 18 months, respectively, after a viral illness and salicylate therapy. Both had fasting hypoglycemia and hypoketonemia. At the time of the acute episode and after ingestion of a medium-chain triglyceride load, one of them excreted large amounts of abnormal metabolites derived from the omega- and (omega-1)-oxidation of medium-chain fatty acids. Medium-chain acyl-CoA dehydrogenase activity was lower than 20% of control values in fibroblasts from both patients. This enzyme defect should be considered in children with a Reye-like syndrome with these distinctive manifestations.

Multiple acyl-CoA dehydrogenase deficiency occurring in pregnancy and caused by a defect in riboflavin metabolism in the mother. Study of a kindred with seven deaths in infancy: Value of riboflavin therapy in preventing this syndrome.

Seven infants in one kindred died: one was stillborn; the others, who were floppy at birth and were breast-fed, developed a disorder with the odor of sweaty feet and died in early infancy. In two further pregnancies, 3-hydroxvisovaleric, glutaric, and C6-C10-dicarboxylic acids were demonstrated in the mother's urine during the seventh month. Riboflavin therapy in the last trimester of pregnancy and a riboflavin-rich diet given the infants prevented this syndrome. The presence of abnormal erythrocyte glutathione-reductase activity in the mother while she excreted normal amounts of riboflavin in her urine indicates a probable disorder of riboflavin metabolism resulting in multiple acyl-CoA dehydrogenase deficiency.