Keith B. Hammond

Efficacy of statewide neonatal screening for cystic fibrosis by assay of trypsinogen concentrations.

BACKGROUND To evaluate the feasibility and efficacy of measuring immunoreactive trypsinogen in blood to screen for cystic fibrosis, we performed this test in 279,399 newborns in Colorado from 1982 to 1987. METHODS Immunoreactive trypsinogen was measured in dried blood spots when the infants were 1 to 4 days old; if the level was elevated (greater than or equal to 140 micrograms per liter), the measurement was repeated (mean age, 38 days); if the level was again elevated, sweat testing was performed (mean age, 49 days). For the second test, two cutoff levels (120 and 80 micrograms per liter) were evaluated. RESULTS We found an incidence of cystic fibrosis of 1 in 3827 (0.26 per 1000), with 3.2 newborns per 1000 requiring repeat measurement. When adjusted for race and compliance with testing, the incidence among the white infants (1 in 2521) was close to the expected incidence. The false positive rate with the initial cutoff level (92.2 percent) was similar to the rate found in neonatal screening programs for other diseases. False negative results occurred because of laboratory error or changes in procedure (three infants) and trypsinogen concentrations lower than the initial cutoff level (three infants) or lower than the remeasurement cutoff level of 120 micrograms per liter (one infant). Sweat tests were negative in 168 infants with an elevated initial trypsinogen level but a level below 80 micrograms per liter on remeasurement, confirming the value of 80 micrograms per liter as an appropriate cutoff for repeat-test results. Overall, 95.2 percent of the infants with cystic fibrosis (95 percent confidence interval, 85 to 99 percent) who did not have meconium ileus could be identified with the use of a trypsinogen cutoff level of 140 micrograms per liter on initial testing and 80 micrograms per liter on repeat testing. CONCLUSIONS Statewide screening for cystic fibrosis based on measurements of immunoreactive trypsinogen in dried blood spots is feasible and can be implemented with acceptable rates of repeat testing and false positive and false negative results.

Prospective, long-term study of fat-soluble vitamin status in children with cystic fibrosis identified by newborn screen☆☆☆★

OBJECTIVE To prospectively evaluate the biochemical status of vitamins A, D, and E in children with cystic fibrosis (CF). SUBJECTS A total of 127 infants identified by the Colorado CF newborn screening program. DESIGN Vitamin status (serum retinol, 25-hydroxy vitamin D, ratio of alpha-tocopherol/total lipids) and serum albumin were assessed at diagnosis (4 to 8 weeks), ages 6 months, 12 months, and yearly thereafter, to age 10 years. RESULTS Deficiency of 1 or more vitamins was present in 44 (45.8%) of 96 patients at age 4 to 8 weeks as follows: vitamin A 29.0%, vitamin D 22.5%, and vitamin E 22.8%. Of these patients with initial deficiency, the percent that was deficient at 1 or more subsequent time points, despite supplementation, was vitamin A 11.1%, vitamin D 12.5%, and vitamin E 57.1%. Of the initial patients with vitamin sufficiency, the percent who became deficient at any time during the 10-year period was as follows: vitamin A 4.5%, vitamin D 14.4%, and vitamin E 11.8%. The percent of patients deficient for 1 or more vitamins ranged from 4% to 45% for any given year. CONCLUSIONS Despite supplementation with standard multivitamins and pancreatic enzymes, the sporadic occurrence of fat-soluble vitamin deficiency and persistent deficiency is relatively common. Frequent and serial monitoring of the serum concentrations of these vitamins is therefore essential in children with CF.

Early bacteriologic, immunologic, and clinical courses of young infants with cystic fibrosis identified by neonatal screening

To understand better the events associated with the initiation of lung disease in young children with cystic fibrosis (CF), we prospectively performed a longitudinal study examining the early bacteriologic, immunologic, and clinical courses of 42 children with CF diagnosed after identification by neonatal screening. Serial evaluations included history and physical examination, chest radiographs, throat cultures for bacteria, and determinations of serum immunoglobulin levels and circulating immune complexes. At a mean follow-up age of 27 months, 19% of the children had serial throat cultures positive for Pseudomonas aeruginosa; the first positive culture was found at a mean age of 21 months. In three infants the initial P. aeruginosa isolates were mucoid. As determined by typing with a DNA probe, serial P. aeruginosa isolates from each patient were identical over time but were genetically distinct from isolates recovered from other patients. Of 11 infants with P. aeruginosa, nine (82%) had previous isolates of Staphylococcus aureus or Haemophilus influenzae; all had received prior antibiotic therapy. In comparison with other infants with CF, children with P. aeruginosa grown on serial throat cultures more frequently had daily cough (p less than 0.01), lower chest radiograph scores (p less than 0.05), and elevated levels of circulating immune complexes (p less than 0.01). None of the study infants had persistent hypogammaglobulinemia or hypergammaglobulinemia. We conclude that (1) S. aureus and H. influenzae remain the isolates most frequently recovered from infants with CF; (2) initial recovery of P. aeruginosa by throat culture is often preceded by the onset of chronic respiratory signs; (3) elevations of circulating immune complexes can occur early, often after the initial recovery of P. aeruginosa; and (4) early P. aeruginosa isolates are genetically distinct, demonstrating the lack of cross-colonization in this newborn population.

Pancreatic insufficiency, growth, and nutrition in infants identified by newborn screening as having cystic fibrosis

To evaluate the impact of early pancreatic insufficiency on growth and nutritional status in cystic fibrosis, we studied 49 infants identified by a newborn screening program. Pancreatic insufficiency, determined by increased 72-hour fecal fat excretion, was present in 59% (23/39) of infants at diagnosis (7.0 +/- 0.8 weeks; mean +/- SEM). Before initiation of pancreatic enzyme replacement, growth and nutritional status of pancreatic-insufficient (n = 16) and pancreatic-sufficient (n = 13) infants were compared. Pancreatic-insufficient infants gained less weight from birth to diagnosis (13.4 +/- 3.4 vs 22.3 +/- 4.0 gm/day; p = 0.05), had decreased triceps skin-fold thicknesses (4.5 +/- 0.3 vs 6.1 +/- 0.4 mm; p less than 0.005), and had lower blood urea nitrogen (3.07 +/- 0.42 vs 4.62 +/- 0.65 mg/dl; p = 0.02) and albumin (2.99 +/- 0.14 vs 3.54 +/- 0.14 gm/dl; p less than 0.01) levels despite higher gross calorie (154 +/- 8 vs 116 +/- 13 kcal/kg per day; p less than 0.01) and protein intakes (2.81 +/- 0.21 vs 2.14 +/- 0.33 gm/kg per day; p = 0.03). Fecal nitrogen loss was correlated with fat loss (r = 0.79; p less than 0.001). Fat malabsorption was present in 79% (30/38) and 92% (33/36) of infants tested at 6 months and 12 months of age, respectively, indicating that pancreatic insufficiency persists and increases in frequency throughout infancy. We conclude that pancreatic insufficiency is prevalent in young infants with cystic fibrosis and has a significant impact on growth and nutrition.

Clinical evaluation of the macroduct sweat collection system and conductivity analyzer in the diagnosis of cystic fibrosis.

The purposes of this study were to compare sweat tests used in diagnosing cystic fibrosis (CF), as performed with the Macroduct collection system, with those utilizing the more laborious quantitative pilocarpine iontophoresis test (QPIT), and to ascertain the efficacy of the Sweat-Chek conductivity analyzer in eliminating some possibly unnecessary chloride analyses. A Macroduct sweat test was performed on one arm and a QPIT on the other on 1090 patients, 93 of whom had CF. Of these, 514 patients (43 with CF) also had a conductivity determination on the Macroduct sweat sample. All subjects were referred to the laboratory of one of us (K.B.H.) for sweat testing. Of the QPIT samples, 0.7% were inadequate, as were 6.1% of those from the Macroduct system. When sodium and chloride concentrations from the two tests were compared, the standard errors of the estimate were 3.90 and 3.85, respectively. Agreement within 8 mEq/L could then be expected with 95% confidence limits. With use of the Sweat-Chek analyzer, no patient with CF was found to have a conductivity of less than 90 mmol/L, whereas 430 (91%) of the non-CF subjects had a conductivity of less than 50 mmol/L. None of those 430 subjects had a sweat chloride value > 32 mmol/L. We conclude that the Macroduct collection system provides results equally as satisfactory as those provided by the QPIT and that the Sweat-Chek analyzer frequently eliminates the necessity of measuring chloride concentrations.

Hypoalbuminemia at diagnosis as a marker for severe respiratory course in infants with cystic fibrosis identified by newborn screening.

in treating central nervous system manifestations of Lyme disease. Meningeal symptoms (headache, stiff neck) are usually suppressed rapidly by prednisone administered orally; however, it has not been shown that such treatment hastens resol~ition of neurologie deficits or improves outcome. 2 One of our patients improved without eortieosteroid therapy. The other, who had more severe manifestations of pseudotumor~ received prednisone but has had persistent signs and symptoms of increased intracranial pressure. The limited data gathered from these patients, as well as the association of steroid use or withdrawal in precipitating pseudotumor cerebri, do not support the routine use of corticosteroids in patients with pseudotumor and Lyme disease. Acetazolamide was effective in controlling the intracranial hypertension in these patients. Intravenously administered penicillin also seemed beneficial.

Immunoreactive trypsinogen levels in infants with cystic fibrosis complicated by meconium ileus

Abstract To examine abnormalities in immunoreactive trypsinogen (IRT) in infants with cystic fibrosis (CF) and meconium ileus (MI) and to evaluate the utility of IRT as a diagnostic aid in MI, we compared IRT in 19 infants with CF and MI to values in normal infants and in 91 infants with CF without MI. Infants with CF without MI were identified between 1982–1989 through a statewide screening program based on IRT measurements ( n =83) or through clinical presentation ( n = 8). Infants with MI were identified through clinical presentation during the same period. The IRT level of MI patients as a group (195±23 ng/ml) was greater than the cutoff value for IRT in normal infants (140 ng/ml, corresponding to the 99.7th percentile for infants less than 20 days of age; P P

718 ABNORMALITIES IN FAT-SOLUBLE VITAMIN STATUS AT THE TIME OF DIAGNOSIS IN INFANTS WITH CYSTIC FIBROSIS IDENTIFIED BY NEWBORN SCREEN

We have previously reported evidence of early protein malnutrition in some infants with cystic fibrosis (CF) identified by the newborn screening method using serum immunoreactive trypsinogen. We now report very early abnormalities in the status of fat-soluble vitamins in 6 of 10 infants (mean age, 5.7 weeks; range, 3-8 weeks) with CF identified by screening in 1984. Plasma retinol (PR) and γ and α-tocopherol (α-Toc) levels were measured by HPLC. Retinol binding protein (RBP) levels were measured by radial immunodiffusion. Total serum lipids, serum albumin, calcium, and phosphorus were measured by standard methods. Four infants had low levels of serum albumin (<3.2 g/dL), low levels of α-Toc (<3.0 μg/ml), and low total tocopherols/total serum lipid ratios (<0.6 mg/gm). Three of these infants had RBP levels of 1.5 mg/dl (normal, 1.4-3.3 mg/dL). PR levels were low in 5 infants (<20 μg/dL). PIVKA-II assays (by plasma immunoelectropheresis before and after BaCC3 absorption, representing noncarboxylated prothrombin specific for Vitamin K deficiency) were negative in all infants. Serum calcium and phosphorus levels were not low, suggesting adequate Vitamin D status. We conclude that as early as 6 weeks of age, some infants with CF have biochemical deficiencies of the fat-soluble vitamins A and E. However, these infants, all of whom had parenteral Vitamin K prophylaxis at birth, were not Vitamin K deficient.

NUTRITIONAL AND PULMONARY ABNORMALITIES AT THE TIME OF DIAGNOSIS OF CYSTIC FIBROSIS IN INFANTS IDENTIFIED BY NEONATAL SCREENING

The status of patients with cystic fibrosis (CF) prior to overt symptomatology is poorly described. Early identification of CF infants through neonatal screening using the immunoreactive trypsinogen assay followed by sweat testing allowed us to evaluate CF patients prior to onset of overt symptoms. Seventeen CF infants (mean age 5.7 weeks) without acknowledged symptoms were studied prior to medical intervention to determine their nutritional and pulmonary status. Eight infants decreased weight percentile from birth to diagnosis despite adequate caloric intake (mean intake 160 cal/kg/day). Triceps skin fold thicknesses were less than the 50th percentile for all infants measured. Three infants had significantly low serum albumin and/or total protein values. Even more strikingly, the groups mean level of prealbumin, a rapid-turnover protein, was significantly (p<.05) lower than that of age-matched normals. In addition, two of 12 infants became hypoxic during sleep, decreasing their transcutaneous PO2 to less than 40 torr. Four infants without previously acknowledged lung disease had abnormal chest x-rays, showing hyperexpansion, linear markings of bronchial cuffing and infiltrates. We conclude that abnormalities of growth, protein metabolism and pulmonary function exist in infants with CF prior to the onset of marked clinical symptomatology. We speculate that some of these deficits may be reversible with medical intervention.