A preliminary report on urinary BT-PABA/PAS excretion index, serum pancreatic isoamylase and faecal chymotrypsin tests of pancreatic dysfunction in Sowetan Africans

Abstract

The steady increase in chronic pancreatitis among black Africans at Soweto, RSA, in the past 40 years necessitates an objective and non-invasive test to detect the disease at an early stage. Given the biphasic nature of the disease — secretory hyperfunction with periodic active inflammatory episodes followed by steady exocrine impairment — we assessed three potential aids. Urinary BT-PABA/PAS excretion index (PEI), serum pancreatic isoamylase (PIA) and faecal chymotrypsin activity (FCA) were measured in the following groups: 16 outwardly healthy hospital workers, 16 consecutive patients with calcifying chronic pancreatitis and 19 with abdominal pain ascribed to other conditions (disease controls). (1) Healthy controls had lower PEI than those at Manchester, UK, or Madras, India, from subclinical acinar loss — as shown by lower PABA recovery whereas intestinal absorptive capacity was maintained, as shown by recovery of PAS. (2) Using the popular cut-off for PEI (0.75) only 9 of 14 patients with chronic pancreatitis were identified (sensitivity 64%, 2 tests unsatisfactory), while a value of less than 0.54, the mean −2 S.D. in local controls, yielded sensitivity of 50%. (3) If PEI of less than 0.75 or PIA outside the reference range was taken to indicate the disease, 5 of 9 disease controls would have been classed as chronic pancreatitis (among those with both tests satisfactory): retrospective ultrasound scans did not identify these. (4) Although FCA was less than the preselected cut-off, 5 units/g, in every patient with chronic pancreatitis (100% sensitivity) its poor predictive value was indicated by low specificity: subnormal levels in 4 of 14 and 6 of 16 healthy controls or disease controls, respectively, most of whom had near-normal values of PEI, PIA or both. (5) Collectively, these results suggest a high frequency of subclinical chronic pancreatitis at Soweto, but also that the combination of tests required to identify it may prove impractical — whether in field surveys or hospital practice.