Serum salivary amylase in cystic fibrosis [letter].

We found that cystic fibrosis (CF) patients with pancreatic insufficiency (PI) had 
a statistically lower total serum amylase level than normal subjects, but 
all values were still within the normal range. Although we found 
that the absolute amount of salivary amylase, in the serum of 
patients with CF and PI, was the same as that for 
normal subjects, the percent of contribution was considerably higher. We found 
that the pancreas contributed approximately 23% of the total serum amylase 
in CF patients with PI, a value very similar to the 
34% amount found by Kamaryt et al. We also found, as 
did Davidson et al., that CF patients without PI had higher 
total serum amylase values than did normal subjects. Thus, we feel 
that Davidson et al. have misinterpreted the results of our previous 
study and, in fact, we feel that Davidson et al. have 
essentially confirmed our previous work by suggesting that CF patients with 
pancreatic insufficiency have an increased salivary amylase for reasons yet unknown. 
Our experience has shown that, indeed, the pancreatic portion is first 
increased and then decreases as the patient with CF and apparent 
normal pancreatic function progresses, with time, toward pancreatic insufficiency. However, the 
changes in serum amylase values in patients with CF are on 
the average due to changes in the pancreatic contribution to the 
serum and as expressed as a mean was highly significantly different 
for both normal and abnormal pancreatic function. The second important point 
of our paper was that this mean variation occurred in serum 
samples from patients with CF that had total amylase values within 
the normal test range. The serum salivary isoamylase in both normals 
and patients with CF and PI had a higher serum salivary 
percent. 