1. What, if any, is the role of laboratory tests in the diagnosis of CP, especially of uncertain cases ?

Tumor MarkersFNAC

Laboratory Investigations for Chronic Pancreatitis

Tests for Structural Abnormalities

Tests for Functional Abnormalities

USS, CT, MRCP, EUS

Exocrine Function

Endocrine FunctionOnly for documentation & therapy

Direct Stimulation Tests Indirect Testspancreatic enzymes in duodenal samples after meal products of digestive enzyme action on ingested substrates; the measurement of pancreatic enzymes in the stool; the measurement of the plasma concentration of hormones

Genetic studies for aetiology

Indirect Tests

• Lundh Test Meal • Fecal Fat

– Sudan III Staining

• Chymotrypsin or Elastase-1 in Stool

• Bentiromide Test• Fluorescein

Dilaurate (Pancreolauryl) Test

• Serum trypsinogen• Other Tests

– triglyceride and cholesteryl breath tests;

– H2 and CO2 breath tests;

– the dual label Schilling test;

– plasma measurements of pancreatic polypeptide and amino acids.

Malabsorption occurs only when functional capacity is reduced to 5% to 10% of normal. most function tests will be positive only in far-advanced disease and are less accurate in early chronic pancreatitis.

DiMagno EP, N Engl J Med 1973; 288:813.

Routine Laboratory Tests

• Not generally useful in making a diagnosis of CP. – The leukocyte count: usually normal in the absence of

infection. – Alkaline phosphatase or bilirubin may be abnormal:

• compression of the intrapancreatic bile duct by a pseudocyst or fibrosis within the head of the pancreas.

– Serum amylase or lipase may be elevated: • acute exacerbations: elevations are modest. Neither routinely

present nor diagnostic for chronic pancreatitis. • Pseudocyst, • Pancreatic ductal stricture, or • Internal pancreatic fistula.

– Serum albumin and calcium may be decreased. • chronic alcoholic patients, in whom one may malnutrition, anemia

with macrocytosis, thrombocytopenia, and leukopenia.

Do We Have A Gold Standard?

• Sensitivity, specificity, and accuracy of diagnostic tests is measured against a “gold standard”.

• In the case of chronic pancreatitis, the gold standard is pancreatic histology. – the histologic changes not uniform throughout

the gland, so that a small biopsy specimen may not give a complete picture of the presence or absence of disease.

– obtaining pancreatic tissue on a routine basis is risky and seldom performed.

Substitute Gold Standard?

• Prolonged follow-up. – Most series have not followed patients

diagnosed with early chronic pancreatitis or possible early chronic pancreatitis (patients in whom diagnostic tests are not unequivocally positive) for long enough to establish the presence or absence of chronic pancreatitis with certainty.

• Apart from sensitivity and specificity of test, the doctor must consider the availability, cost, and risk of each of these tests to maximize benefit and minimize risk.

Direct Tests: Virtual Gold Standard

• The principle – Maximal volume, bicarbonate secretion,

and enzyme secretion are related to the functional mass of the pancreas.

• The secretion stimulated by constant intravenous infusion. – CCK-octapeptide (40 ng/kg/hour) and – Secretin (0.25 CU/kg/hour).

Direct Tests

• Both the stomach and duodenum are intubated.– The gastric tube: removes gastric secretions

• Interfere with the ability to measure volume and bicarbonate secretions from the pancreas

• Low pH may also alter pancreatic enzyme activity. – The duodenal tube:

• Infusion of a nonabsorbable marker (such as cobalamin or polyethylene glycol (PEG) allows the quantitation of secretions without the need for complete aspiration of secretions).

• Collection of pancreatic secretions. Niederau C, Gastroenterology 1985; 88:1973.

Direct Tests

• Measure– Volume – Bicarbonate – Amylase, trypsin, chymotrypsin, and lipase

• Measurements are corrected for percentage recovery.

• 83% sensitive and 89% specific. Heiji HA, Scand J Gastroenterol 1986; 21:35.

• False-positive results may occur in patients with celiac sprue and diabetes mellitus.

Do We Need Direct Tests?

• These tests are performed at hardly any centre in India and are generally not available.

• In most comparisons with pancreatography (ERP), direct hormonal stimulation tests appear to be slightly more sensitive for the diagnosis of chronic pancreatitis.

• The values for sensitivity in studies range from 74% to 97%, with specificity ranging from 80% to 90%.

• In four studies, the percentage of patients with an abnormal hormonal stimulation test and a normal pancreatogram ranged from 3% to 20%.

Niederau C, Scand J Gastroenterol 1984; 19:161.Braganza JM, Gastroenterology 1982; 82:1341.

Girdwood AH, Dig Dis Sci 1984; 29:721. Malfertheiner P, Hepatogastroenterology 1986; 33:110.

Lankisch PG, Pancreas 1996; 12:149. Bozkurt T, Gut 1994; 35:1132.

Do We Need Direct tests??

• Follow up of patients whose diagnosis was based solely on an abnormal hormonal stimulation test, found chronic pancreatitis developing on follow-up in 90%.

Lankisch PG, Pancreas 1996; 12:149. Lambiase L, Gastroenterology 1993; 104:A315.

• In patients with moderate or severe histological changes of chronic pancreatitis, the sensitivity of hormonal stimulation testing was 79%. In this same group of patients, the sensitivity of pancreatography was 66%.

Hayakawa T, Am J Gastroenterol 1992; 87:1170.

Do We Need Direct tests??

• Limitations: not standardised, – The normal ranges for the test need to be established at

each center performing the test. – Test is available if at all only at a very few referral centers – Secretin, is not easily available.– Expensive, and time consuming. – False-positive test results have been reported in patients

with diabetes, Billroth II gastrectomy, celiac sprue, cirrhosis, and those recovering from an attack of acute pancreatitis.

• This test is most useful in patients with presumed chronic pancreatitis without easily identifiable structural and functional abnormalities on more widely available imaging tests.

Function Testing In Diagnosing CP

• Abnormal function test results alone are not diagnostic of CP– Mayo Clinic Scoring System

• Layer P. Gastroenterology 1994;107: 1481–1487.– Lu¨neburg Clinic criteria

• Lankish PG. Surg Clin North Am 1999;79:815–827.– An abnormal secretin test does meet diagnostic criteria for

CP in the Japan Pancreas Society criteria • Homma T. Pancreas 1997;15: 14–15

• In each of these diagnostic systems, CP is diagnosed by a single “diagnostic” imaging study (e.g., histology, typical CT scan, ERCP, or ultrasound identifying calcifications).

Babak Etemad. GASTROENTEROLOGY 2001;120:682–707

Classification Of CP

• "Big-duct" disease (No role of lab tests in diagnosis) – Dilation of PD visible on ultrasound, CT, or ERP– Functional abnormalities +++– Often due to alcohol abuse– Therapy focus: decompress dilated PD.

• “Small-duct" disease (No role of indirect tests)– Normal or near-normal US, CT, or ERP. – Exocrine or endocrine insufficiency uncommon. – More frequently idiopathic, – Therapy focus: medical rather than surgical or endoscopic

attempts to decompress the pancreatic duct.

2. Can Lab tests help differentiate CP from cancer ?

Can Lab tests help differentiate CP from cancer ?

• Several tumor markers such as – Peanut agglutinin, pancreatic oncofetal antigen, DU-PAN-2,

carcinoembryonic antigen, alpha -fetoprotein, CA-50, SPan-1, and tissue polypeptide antigen. (Cigarette smoking, DDT exposure)

– Only one has practical utility: CA 19-9. • Unsuitable for screening• Valuable adjunct in the diagnosis, prognosis, and monitoring

of pancreatic cancer.– In the presence of jaundice, and especially with cholangitis, very

high values can be found in the absence of malignancy (false-positive results).

– In addition, patients with a Lewis blood group phenotype (-a,-b) do not express the CA 19-9 antigen.

• In a recent study, using a cutoff of 37 U/mL, sensitivity and specificity were 86% and 87%, respectively.

3. What is the list and cost of suggested tests ?

Suspected CP

Plain abdominal radiography (Rs 100/-), Abdominal ultrasonography (Rs 250/-), Serum Trypsin (Rs 6400).

DiagnosisNo Diagnosis

DiagnosisNo Diagnosis

CT Scan (Rs 2000/-)

DiagnosisNo Diagnosis

Direct Function Tests* (?)

DiagnosisNo Diagnosis

ERCP (Rs 2500/-)

Follow UpMRCP, EUS Value unknown(Rs 4000/- each)

No further tests for diagnosis.

SuggestedDiagnostic Strategy

Stool fat by Sudan III staining (Rs 350/-)Blood Sugar (F & PP: Rs 120/-)CA 19,9 (Rs 850/-)

* If available

Conclusions

• Large number of pancreatic function tests are available.• In choosing a diagnostic test for CP, physician must consider

sensitivity, specificity, accuracy as well as cost, risk, and availability.

• the accuracy of the diagnostic tests depends on the stage and etiology of the disease.

• A typical clinical presentation and pancreatic calcification on plain X-ray / US scan may be enough to make diagnosis in many cases of CCPT and CAP.

• Inexpensive and risk free tests are sufficient for advanced disease (plain abdominal radiography, serum trypsin, fecal fat, fecal elastase, or serum glucose).

• In early cases, one may need tests that are more sensitive but expensive (CT, ERCP, EUS, MRCP), risky (ERCP), or not widely available (direct pancreatic function tests).

Do We Need Direct tests??

• Follow up of patients whose diagnosis was based solely on an abnormal hormonal stimulation test, found chronic pancreatitis developing on follow-up in 90%.

Lankisch PG, Pancreas 1996; 12:149. Lambiase L, Gastroenterology 1993; 104:A315.

– May identify a small group of patients with CP who have functional abnormalities of stimulated secretion but who do not (yet) have structural abnormalities identifiable on ERCP.

– Conversely, most of these studies also document patients with a normal direct test and an abnormal pancreatogram.

• This group of patients is generally less common, averaging less than 10% in several studies.

• Long-term follow-up in a small group of these patients noted chronic pancreatitis developing in 0% to 26%.

• These studies point out that when the two tests disagree, hormonal stimulation testing appears to be somewhat more sensitive and specific than pancreatography.

Which Laboratory Test to Use?

• Large number and variety of tests for CP; Selection depends on– the clinical question – the characteristics of the test. – and availability of the test

• Malabsorption occurs only when functional capacity is reduced to 5% to 10% of normal. – most function tests will be positive only in far-

advanced disease and are less accurate in early chronic pancreatitis.

DiMagno EP, N Engl J Med 1973; 288:813.

Routine Laboratory Tests

• Hyperglycemia is seen when diabetes develops in advanced chronic pancreatitis. – Rarely used as a diagnostic test– Diabetes is a common disease, can

coexist!

Variations

• Collection of secretin-stimulated pancreatic secretions at the time of ERP by placement of a catheter in the pancreatic duct (the so-called intraductal secretin test)

• Not standardized and does not appear to be as accurate as standard direct pancreatic function testing.

Gastroenterologic Endoscopy, Sivak MV (ed): 2nd ed. Philadelphia, WB Saunders, 2000, p 1116.

Fecal Fat

• A 72-hour collection of stool while the patient is consuming a 100 g/day fat diet provides the best evidence of fat maldigestion. 7% or less of ingested fat appears in the stool.

• The semi-qualitative analysis of fecal fat can also be performed with a Sudan III stain of a random specimen of stool. – More than six globules per high-power field is considered to be

positive but, again, the patient must be ingesting adequate fat to allow measurable steatorrhea.

– Sudan III staining of stool is positive only in patients with substantial steatorrhea.

• Measurement of fecal fat is not useful in the diagnosis of mild or moderate disease. And the test is not specific for pancreatic disease.

Chymotrypsin or Elastase-1 in Stool

• Fecal chymotrypsin is abnormal in most patients with chronic pancreatitis and steatorrhea. – False-positive tests have been reported in other malabsorptive

conditions (sprue, Crohn's disease), in diarrheal diseases when the stool is diluted, and in severe malnutrition.

– The test is normal in the absence of steatorrhea, so the test is positive only in advanced chronic pancreatitis.

• Fecal elastase has advantages over fecal chymotrypsin in that it is very stable in passage through stool and easy to measure. – the test accurate in the presence of steatorrhea but inaccurate in

less advanced chronic pancreatitis. – the test may be falsely abnormal in other diseases causing

steatorrhea, such as short bowel syndrome or small bowel bacterial overgrowth.

Bentiromide Test

• The synthetic peptide NBT-PABA is specifically cleaved by the pancreatic endopeptidase, chymotrypsin, to NBT and PABA. – PABA is absorbed in the intestine, conjugated in the liver, and

excreted in the urine. It can be measured in either the serum or the urine.

• Limitations– In patients with severe pancreatic insufficiency and

malabsorption, the sensitivity is 80% to 90%; In mild to moderate impairment, sensitivity is low ~ 40%.

• Administering free PABA on a separate day or giving14C-PABA or paraminosalicylic acid simultaneously with NBT-PABA may identify patients with abnormal NBT-PABA test result caused by mucosal disease of the small bowel.

– Erroneous reults in • Prior gastric surgery, small bowel disease, liver disease, renal

insufficiency, the use of certain drugs (acetaminophen, benzocaine, chloramphenicol, lidocaine, phenacetin, procaine, sulfonamide, sulfonylurea, and thiazides), and after certain foods (prunes and cranberries)

Fluorescein Dilaurate (Pancreolauryl) Test

• Fluorescein dilaurate is given in the middle of a breakfast meal. It is an ester, poorly soluble in water, that is hydrolyzed by carboxylesterase into lauric acid and free water-soluble fluorescein. – The fluorescein is readily absorbed into the intestine,

partly conjugated in the liver, and excreted in the urine. – Urine is collected for 10 hours after breakfast, and the

fluorescein excreted in the urine is measured.

• Pancreolauryl test is highly sensitive and specific for advanced pancreatic disease and less so for mild and moderate disease.

Serum trypsinogen (trypsin)

• Very low levels of serum trypsinogen (<20 ng/mL) are reasonably specific for chronic pancreatitis, but levels this low are seen only in advanced chronic pancreatitis with steatorrhea.– is inexpensive, widely available, and risk-free,

although it is accurate only in long-standing and far-advanced chronic pancreatitis.

– not decreased in patients with other forms of steatorrhea, but low levels of serum trypsinogen may be seen in patients with pancreatic ductal obstruction, including malignant obstruction.

Other Tests

• Include– triglyceride and cholesteryl breath tests; – H2 and CO2 breath tests; – the dual label Schilling test; – plasma measurements of pancreatic polypeptide and

amino acids.• None of these tests have been shown to have

increased sensitivity over the indirect tubeless tests described previously.

• Many of these tests require radioactive isotopes or expensive equipment making their utility less desirable.