A 24-Hour-Old Infant Is Tested for Quantitative Sweat Chloride Because

A 24-hour-old infant is tested for quantitative sweat chloride because her older brother was diagnosed with cystic fibrosis.After iontophoresis of pilocarpine nitrate and collection of sweat,the sample is analyzed by coulometric titration.The value of the infant's sweat chloride was 23 mmol/L (reference interval: 29 mmol/L) .The next day,the infant's physician calls the laboratory to report that the infant has difficulty breathing and that the parents report the infant's skin tasted salty.The physician is considering a diagnosis of cystic fibrosis.What type of error has likely occurred?

A) The specimen likely evaporated before being analyzed in the laboratory.
B) The infant was tested at too young of an age for accurate results to be obtained.
C) The specimen was collected over a site of a rash and contaminated with serous fluid.
D) The infant's average sweat rate was too high to obtain accurate results.