Lr. Schiller et al., DIAGNOSTIC-VALUE OF FASTING PLASMA PEPTIDE CONCENTRATIONS IN PATIENTSWITH CHRONIC DIARRHEA, Digestive diseases and sciences, 39(10), 1994, pp. 2216-2222
To evaluate the utility of screening for multiple gastrointestinal pep
tides in the evaluation of patients with chronic diarrhea, we studied
193 patients referred for evaluation of chronic diarrhea and eight pat
ients with known peptide-secreting tumors as a reference group. Eastin
g plasma samples were assayed for motilin, neurotensin, pancreatic pol
ypeptide, somatostatin, substance P, vasoactive intestinal polypeptide
, gastrin-releasing peptide, and calcitonin during a protocol evaluati
on for causes of chronic diarrhea. Although none of the referred patie
nts were found to have tumors, abnormal levels of one or more peptides
were found in 86 of 193 patients (45%). Abnormal plasma peptide level
s were sometimes as high in these patients as in patients with known p
eptide-secreting tumors and would have led to mistaken diagnoses of tu
mors much more often than they would have led to correct diagnoses. Th
e positive predictive value of elevation of any assayed peptide was <2
% at realistic prevalence rates for peptide-secreting tumors; the nega
tive predictive value of a series of normal results was >99%, but much
of this was due to the rarity of these tumors. Patients with chronic
diarrhea should not be screened routinely with a panel of plasma pepti
de assays in an effort to detect tumors; instead, peptide levels shoul
d be ordered selectively. Elevated fasting concentrations of the plasm
a peptides measured in this study are most likely epiphenomena due to
diarrhea and should not be the sole basis for invasive diagnostic or s
urgical management of these patients.