Indirect measurements of sweat electrolyte concentration in the laboratory diagnosis of cystic fibrosis.

AIM: To investigate whether analytical methods based on the colligative physical chemical properties of ions or solutes in sweat are less effective than the specific measurement of electrolytes in the diagnosis of cystic fibrosis (CF). METHODS: A single sweat sample was collected (Macroduct) from each of 211 infants and children, of whom 57 had CF, for the measurement of sodium, chloride, osmolality, and conductivity. RESULTS: The ranges within which CF and non-CF individual values overlapped (equivocal ranges), were wider for sodium and osmolality measurement than for chloride or conductivity. Neither of the latter two measurements provided a discriminatory advantage over the other. The utilisation of broadly based age related ranges for non-CF control subjects served to improve the discriminatory power of all four measurements to an extent that, in this cohort, both chloride and conductivity provided complete discrimination. CONCLUSION: Sweat conductivity is as effective as chloride measurement in the laboratory diagnosis of CF.

Prognosis in cystic fibrosis treated with continuous flucloxacillin from the neonatal period.

All newborn infants in East Anglia are screened for cystic fibrosis by blood immunoreactive trypsin assay at 7 days. Thirty eight infants with cystic fibrosis were randomised to treatment with either continuous oral flucloxacillin 250 mg/day (group P, n = 18) or with episodic antimicrobials as clinically indicated (group E, n = 20). Their progress was monitored from diagnosis to 24 months by a nurse coordinator who visited all infants regularly, at home and in hospital, to collect anthropometric, dietary, clinical, and microbiological data. Mean (range) age of confirmation of diagnosis was 5.7 weeks (1-14 weeks). There was no significant difference in birth weight, genotype, immunoreactive trypsin concentration, neonatal history, symptoms at diagnosis, pancreatic enzyme supplementation, or parental smoking history between the groups. Infants in group E had more frequent cough and a greater number of Staphylococcus aureus isolates than infants in group P. More infants of group E were admitted to hospital, had higher admission rates during the second year (19 v 5), for longer periods (6.4 v 2.2 days), despite receiving more than double the number of courses of antibiotics than group P infants (in addition to flucloxacillin). Continuous prophylactic flucloxacillin from early diagnosis of cystic fibrosis is associated with improved clinical progress during the first two years of life.

Immunoreactive trypsin in acute pancreatitis: elevated levels do not correlate with hyperamylasaemia.

Immunoreactive trypsin (IRT) was measured in the serum of patients presenting with acute pancreatitis (AP) and compared to serum amylase levels. Both were elevated beyond the normal range at presentation (mean IRT 557 +/- 252 micrograms/l, range 181-1000 micrograms/l, mean control IRT 42 +/- 14 micrograms/l, range 15-82 micrograms/l; mean amylase 4500 +/- 3200 IU/l, range 600-10,500 IU/l, control amylase mean 175 +/- 43 IU/l, range 48-320 IU/l). There was minimal correlation between IRT and amylase elevation but both returned to normal at the same rate in patients who recovered. In 2 patients with persistently elevated IRT levels, one was found to have a pancreatic pseudocyst and the other subsequently died from alcoholic haemorrhagic pancreatitis. IRT is no better than amylase as a single diagnostic assay in AP but may be greatly elevated when amylase elevation is minimal. The combination of the two may improve diagnostic accuracy and persistent elevation of IRT may be of prognostic importance.

Screening for cystic fibrosis by died blood spot trypsin assay.

Immunoreactive trypsin was measured in dried blood specimens from 14,000 infants. A second test was performed in 0 . 2% of the population in whom blood trypsin levels were greater than 80 ng/ml. Five infants with cystic fibrosis were then detected, with only one case of persistent hypertrypsinaemia in whom this diagnosis could not be established. No false-negative test results have yet been identified. Seventeen infants with cystic fibrosis were tested inthe first 2 weeks of life, only one of whom had a blood trypsin concentration less than 80 ng/ml.