A hemolyzed preparation of whole blood is mixed

continuously for 5 minutes with a weakly binding cationexchange resin. The labile fraction is eliminated during

the hemolysate preparation and during the binding.

During this mixing, HbA0 binds to the ion exchange

resin leaving GHb free in the supernatant. After the

mixing period, a filter separator is used to remove the

resin from the supernatant. The percent glycosylated

hemoglobin is determined by measuring absorbances of

the glycosylated hemoglobin (GHb) fraction and the total

hemoglobin (THb) fraction. The ratio of the absorbances

of the Glycosylated hemoglobin and the Total hemoglobin

fraction of the Control and the Sample is used to calculate

the percent Glycosylated hemoglobin of the sample.

Normal Reference Values

Normal : 4.5–8.0%

Good control : 8.0–9.0%

Fair control : 9.0–10.0%

Poor control : > 10.0%.

It is recommended that each laboratory establish its

own normal range representing its patient population.

Contents 10 Tests 25 Tests

Ion Exchange Resin 10 × 3 mL 25 × 3 mL

(Predispensed Tubes)

Lysing Reagent 5 mL 12.5 mL

Control (10% GHb) 1 × 1 mL 1 × 1 mL

Resin Separators 10 Nos. 25 Nos.

Storage/Stability

Contents stable at 2–8oC till the expiry mentioned on the

label. Do not freeze. The Resin separators can be removed

on opening the kit and stored at RT.

Reagent Preparation

The ion exchange resin tubes and the lysing reagent are

ready to use.

Reconstitute the control with 1 mL of distilled water.

Allow to stand for 10 min with occasional mixing. The

reconstituted control is stable for at least 7 days when

stored at 2-8oC tightly sealed, and at least 4 weeks when

stored at -20oC. Do not thaw and refreeze.

Sample Material

Whole blood. Preferably fresh and collected in EDTA. GHb

in whole blood is reported to be stable for one week at

2-8oC.

Procedure

Wavelength/Filter : 415 nm (Hg 405 nm)

Temperature : RT

Light path : 1 cm

A. Hemolysate preparation

1. Dispense 0.5 mL lysing reagent into tubes labeled as control (C) and test (T).

2. Add 0.1 mL of the reconstituted control and

well-mixed blood sample into the appropriately

labeled tubes. Mix until complete lysis is evident.

3. Allow to stand for 5 minutes.

B. Glycosylated hemoglobin (GHb) Separation

1. Remove cap from the ion-exchange resin tubes

and label as control and test.

2. Add 0.1 mL of the hemolysate from Step A into

the appropriately labeled Ion exchange resin

tubes.

3. Insert a resin separator into each tube so that the

rubber sleeve is approximately 1 cm above the

liquid level of the resin suspension.

4. Mix the tubes on a rocker, rotator or a vortex

mixer continuously for 5 minutes.

5. Allow the resin to settle, then push the resin

separator into the tubes until the resin is firmly

packed.

6. Pour or aspirate each supernatant directly into

a cuvette and measure each absorbance against

distilled water.

C. Total hemoglobin (THb) fraction

1. Dispense 5.0 mL of distilled water into tubes

labeled as control and test.

Diabetes Mellitus: Laboratory Diagnosis 445

2. Add to it 0.02 mL of hemolysate from Step A into

the appropriately labeled tube. Mix well.

3. Read each absorbance against distilled water.

Calculations

Ratio of Control (RC) = Abs. Control GHb

Abs. Control THb

Ratio of Test (RT) = Abs. Test GHb

Abs. Test THb

GHb in % = Ratio of Test (RT)

Ratio of Control (RC)

× 10 (Value of Control)

Linearity

The glycosylated hemoglobin procedure shows linearity

for GHb levels in the range of 4.0–20.0%.

Notes

Blood samples with hemoglobin greater than 18 g/dL

should be diluted 1 + 1 with normal saline before the assay.

Samples from patients with hemoglobinopathies,

decreased red cell survival times, gross lipemia may show

incorrect results.

Do not use ion exchange resin tubes in case of turbidity

or visible discoloration.

Diabetics with metabolic imbalance may have

extremely high levels of the labile aldimine form. In such

cases the incubation time during hemolysate preparation

may be increased to 15 minutes to ensure elimination of

this instable fraction.

For mean blood glucose level based upon GHbA1/

HbA1c refer to Table 17.4.

Insulin

Normal Values

SI Units

Adult

Fasting level < 17 µU/mL 42–243 pmol/L

or 1.00 mg/L

Newborn 3–20 µU/mL 21–139 pmol/L

Infant < 13 µU/mL < 89 pmol/L

Prepubertal child < 13 µU/mL < 89 pmol/L

Panic levels > 30 µU/mL > 290 pmol/L

Last trimester, amniotic fluid 11.3 µU/mL 78 pmol/L

Insulin is a hormone produced in pancreas by the beta

cells of the islets of Langerhans, regulates the metabolism

of carbohydrates along with liver, adipose, muscle, and

other target cells and is responsible for maintaining a

constant level of blood glucose. The rate of insulin secretion

is determined primarily by the level of blood glucose

perfusing the pancreas and is affected by hormonal status,

the autonomic nervous system, and nutritional status.

Test Significance

This measurement of the insulin secretory response to

glucose may be of value in establishing the diagnosis of

insulinoma and in the evaluation of abnormal carbohydrate

and lipid metabolism. Insulin levels are also helpful in

supporting the diagnosis of diabetes in persons with

borderline abnormalities of the GTT. This determination

is invaluable in the investigation of fasting hypoglycemic

patients and may be useful in the differentiation of islet cell

neoplasms. Insulin levels may be ordered along with GTT.

Clinical Relevance

Increased values are associated with:

A. Insulinoma: diagnosis of insulinoma is based on

1. Association of insulinoma with hypoglycemia

2. Persistent hypoglycemia along with hyperinsulinemia between 2 and 3 hours after injection of

tolbutamide.

3. Failure of C-peptide suppression when plasma

glucose is 40 mg/dL or less. After 100 g of glucose,

normal insulin will rise less than 2 µU/ml to 25 to

231 in half hour, 18 to 276 in one hour, 16 to 166

in 2 hours, 4 to 38 in 3 hours. The results may be

too variable to be of diagnostic importance.

B. Acromegaly

C. Cushing’s syndrome.

Interfering Factors

Falsely increased values are associated with food intake,

obesity, and use of oral contraceptives.

(Method: see Endocrinology chapter).

C-Peptide

Normal Values

SI Units

Qualitative Negative

Quantitative

Adult 68–8200 ng/mL 68–8200 µg/L

or 20 mg/dL

or < 8 µg/mL

Cord blood 10–350 ng/mL 10–350 µg/L

446 Concise Book of Medical Laboratory Technology: Methods and Interpretations TABLE 17.4: For the conversion of glycosylated hemoglobin A1 (GHbA1) to gylcosylated hemoglobin A1c (HbA1c) and to the mean blood

glucose level (MBG)

GHbA1 HbA1c MBG GHbA1 HbA1c MBG GHbA1 HbA1c MBG GHbA1 HbA1c MBG

5.0 3.46 —- 9.0 6.81 141 13.0 10.16 252 17.0 13.51 —-

5.1 3.54 —- 9.1 6.89 144 13.1 10.25 255 17.1 13.60 —-

5.2 3.63 —- 9.2 6.98 146 13.2 10.33 258 17.2 13.68 —-

5.3 3.71 —- 9.3 7.06 149 13.3 10.41 261 17.3 13.68 —-

5.4 3.79 —- 9.4 7.15 152 13.4 10.50 264 17.4 13.85 —-

5.5 3.88 —- 9.5 7.23 155 13.5 10.58 266 17.5 13.93 —-

5.6 3.96 —- 9.6 7.31 158 13.6 10.66 269 17.6 14.02 —-

5.7 4.04 —- 9.7 7.40 160 13.7 10.75 272 17.7 14.10 —-

5.8 4.13 —- 9.8 7.48 163 13.8 10.83 275 17.8 14.18 —-

5.9 4.21 —- 9.9 7.56 166 13.9 10.92 278 17.9 14.27 —-

6.0 4.30 57 10.0 7.65 169 14.0 11.00 280 18.0 14.35 —-

6.1 4.38 60 10.1 7.73 171 14.1 11.08 —- 18.1 14.44 —-

6.2 4.46 63 10.2 7.82 174 4.2 11.17 —- 18.2 14.52 —-

6.3 4.55 65 10.3 7.90 177 14.3 11.25 —- 18.3 14.60 —-

6.4 4.63 68 10.4 7.98 180 14.4 11.34 —- 18.4 14.69 —-

6.5 4.71 71 10.5 8.07 183 14.5 11.42 —- 18.5 14.77 —-

6.6 4.80 74 10.6 8.15 185 14.6 11.50 —- 18.6 14.85 —-

6.7 4.88 77 10.7 8.23 188 14.7 11.59 —- 18.7 14.94 —-

6.8 4.97 79 10.8 8.32 191 14.8 11.67 —- 18.8 15.02 —-

6.9 5.05 82 10.9 8.40 194 14.9 11.75 —- 18.9 15.11 —-

7.0 5.13 85 11.0 8.49 197 15.0 11.84 —- 19.0 15.19 —-

7.1 5.22 88 11.1 8.57 199 15.1 11.92 —- 19.1 15.27 —-

7.2 5.30 91 11.2 8.65 202 15.2 12.01 —- 19.2 15.36 —-

7.3 5.39 93 11.3 8.74 205 15.3 12.09 —- 19.3 15.44 —-

7.4 5.47 96 11.4 8.82 208 15.4 12.17 —- 19.4 15.53 —-

7.5 5.55 99 11.5 8.91 211 15.5 12.26 —- 19.5 15.61 —-

7.6 5.64 102 11.6 8.99 213 15.6 12.34 —- 19.6 15.69 —-

7.7 5.72 104 11.7 9.07 216 15.7 12.42 —- 19.7 15.78 —-

7.8 5.80 107 11.8 9.16 219 15.8 12.51 —- 19.8 15.86 —-

7.9 5.89 110 11.9 9.24 222 15.9 12.59 —- 19.9 15.94 —-

8.0 5.97 113 12.0 9.32 224 16.0 12.68 —- 20.0 16.03 —

8.1 6.06 116 12.1 9.41 227 16.1 12.76 —-

8.2 6.14 118 12.2 9.49 230 16.2 12.84 —-

8.3 6.22 121 12.3 9.58 233 16.3 12.93 —-

8.4 6.31 124 12.4 9.66 236 16.4 13.01 —-

8.5 6.39 127 12.5 9.74 238 16.5 13.09 —-

8.6 6.47 130 12.6 9.83 241 16.6 13.18 —-

8.7 6.56 132 12.7 9.91 244 16.7 13.26 —-

8.8 6.64 135 12.8 9.99 247 16.8 13.35 —-

8.9 6.73 138 12.9 10.08 250 16.9 13.43 —-

MBG in mg/dL = 33.3 x HbA1c value—86

These values are linear in the range of 6.5–13% of HbA1c values

Diabetes Mellitus: Laboratory Diagnosis 447

C-peptide is formed during the conversion of proinsulin

to insulin in the beta cells of the pancreas. It is secreted

into the bloodstream in almost equal concentration with

insulin. Normally, a strong correlation exists between

levels of insulin and C-peptide, except possibly in obese

subjects and in the presence of islet cell tumors.

Test Significance

C-peptide level measurement provides a reliable indication

of beta and secretory function and insulin secretions.

This determination has its most useful application in the

evaluation of endogenous secretion of insulin when the

presence of circulatory insulin antibodies interferes with

the direct assay of insulin. This situation is most likely to

occur in diabetics who have been treated with bovine pork

insulin. The test is also useful in evaluating hypoglycemic

states in identifying surreptitious injection of insulin,

and in confirmation of remission of diabetes mellitus.

Furthermore, monitoring following pancreatectomy for

removal of cancer can provide a means of detecting the

presence of residual tissue.

Clinical Relevance

1. Increased values are associated with endogenous

hyperinsulinism in insulin-dependent diabetic

persons when a high level of insulin is also present.

2. Decreased levels are associated with persons who have

been surreptitiously injecting insulin and who have

both hypoglycemia and high insulin levels.

3. Normal levels are found in persons who have had a

remision of diabetes mellitus.

 (Method: see Endocrinology chapter).

Glucagon

Normal Values

1. 50-200 pg/mL plasma

2. Glucagon response in normal people after a standard

test meal of carbohydrates, fat and protein is a gradual

increase from 92 plus or minus 12 pg/mL to a peak of

125 plus or minus 13 pg/mL.

3. In a glucose tolerance test, glucagon levels will

significantly decline from fasting levels during the

hyperglycemic first hour in normal people.

Glucagon is a peptide hormone produced by alpha cells

of the islets of Langerhans in the pancreas. In the liver,

this hormone promotes glucose production. This action

of glucagon is opposed to that of insulin. The normal

coordinated release patterns of this hormone provide a

sensitive control mechanism for glucose production and

storage. For example, low glucose levels result in release,

whereas conditions of hyperglycemia reduce circulating

glucagon levels to approximately 50% of the amount in the

fasting state.

Kidneys play an important role in the metabolism of

glucagon.

Abnormally high levels of glucagon recede once insulin

therapy begins to control diabetes, and levels slowly revert

to normal in persons on maintenance doses of insulin.

Also, in contrast to the normal glucagon, secretion in

diabetics does not decrease following ingestion of a

carbohydrate meal. However, an arginine infusion causes

greatly increased glucagon secretion in normal persons.

Test Significance

This measurement has clinical significance in two ways.

Glucagon deficiency reflects a general loss of pancreatic

tissue. Compelling evidence for glucagon deficiency

is the failure of glucagon levels to rise during arginine

infusion. Hyperglucagonemia occurs in diabetics, acute

pancreatitis, and in situations where catecholamine

secretion is greatly augmented as in pheochromocytoma

and in the presence of infection.

Clinical Relevance

1. Increased levels are associated with:

a. Acute pancreatitis.

b. Diabetes mellitus. Persons with severe diabetic

ketoacidosis are reported to have levels five times

normal fasting levels despite marked hyperglycemia.

c. Glucagonoma.

d. Uremia.

e. Infections.

f. Pheochromocytoma.

2. Reduced levels are associated with:

a. Inflammatory disease with loss of pancreatic

tissue.

b. Neoplastic replacement of pancreas.

c. Surgical removal of pancreas.

Interfering Factors

Increased levels occur in vigorous exercise and in trauma.

Other Important Tests in Diabetics

Urine — Ketone bodies (present in diabetic

ketoacidosis).

Serum — Cholesterol Can be assessed

 (raised) chemically or

 — Triglycerides } by serum

 (raised) electrophoresis

 — Ketones (raised in presence of ketonuria).

448 Concise Book of Medical Laboratory Technology: Methods and Interpretations Hypoglycemia

By definition means blood glucose levels less than 50 mg%.

Causes of Hypoglycemia

Spontaneous (fasting) Hypoglycemia

1. Excessive insulin

• Insulinoma or insulin-secreting carcinoma

• Erythroblastosis fetalis.

2. Non-endocrine tumor__retroperitoneal fibroma

3. Glycogen storage disease of the liver

4. Malnutrition or malabsorption

5. Adrenocortical or pituitary failure

6. Liver necrosis

7. Hereditary galactosemia

8. Reye’s syndrome and other forms of ketotic

hypoglycemia in children.

Induced Hypoglycemia

1. Excessive insulin:

• Overtreated insulin

• Leucine (includes some islet cell tumors)

• Sulfonyl ureas

• Functional:

– Prediabetic

– Postgastrectomy.

– Hemodialysis with hypertonic glucose

– Idiopathic.

2. Reduced gluconeogenesis.

• Ethanol

• Hypoglycin

• Hereditary fructose intolerance

• Failure of glucagon secretion.

3. Persistent increase of peripheral glucose uptake:

• Failure of catecholamine secretion

• Propranolol blockade of catecholamine effect.

4. Cause uncertain

• Pentamidine.

RAPID DIAGNOSTICS

1. Urine sugar: See urinalysis chapter for dipstick tests.

2. Blood sugar: Various instant blood glucose meters are

available.

Accu-Chek®

(Courtesy: Roche Diagnostics)

Accu-Chek Active System: Virtually Painfree Testing

in 5 Seconds

Things to do. Places to go. Whatever pace you live your life

at, new Accu-Chek Active is with you all the way. In just 5

seconds, Accu-Chek Active delivers highly accurate results,

whenever and wherever you need them. It’s the quickest,

best-looking system ever. If you don’t want diabetes to

slow you down, it’s definitely the way to go.

Accu-Chek Softclix (Fig. 17.1)

The exclusive Accu-Chek Softclix Lancing Device with its

11 variable depth settings and lancet allows you to draw

the minimum amount of blood required.

¾ Virtually pain-free testing

¾ Small, discreet pen-like design

¾ Eleven variable depth settings for maximum comfort

¾ Lancets available on prescription.

Accu-Chek Active Meter

¾ Small, sleek design

¾ Inserting test strip switches on meter automatically

¾ Two hundred test memory with date and time for

automatic recording of results.

Active Glucose Test Strips

¾ Only a tiny drop of blood required

¾ Accurate results in just 5 seconds.

Running a Quality Control Test

For the quality control test, please have the following items

ready (Fig. 17.2):

¾ Your Accu-Chek Active meter with the coding chip

inserted

¾ The pack of Accu-Chek Active Glucose test strips you

took the coding chip from

¾ The Accu-Chek Active Control solutions

¾ Carefully read the pack inserts that came with the test

strips and the control solutions, and select a control

solution

FIG. 17.1: Accu-Chek Softclix

Diabetes Mellitus: Laboratory Diagnosis 449

 

 or depression.

The 1 hour morning aspiration has replaced the

cumbersome and inherently less precise 12 hours nocturnal aspiration.

Method

1. Following a 12 hours overnight fast, the patient is

intubated. Water may be taken until 8 hours prior to

intubation.

2. The residual volume of gastric secretion is measured

and qualitatively examined.

3. Continuous aspiration is begun, preferably manually

with a syringe. Segregate the aspirate into 15 minute

samples. Usually, the first 1 or 2 samples are discarded

to allow the patient to adjust to the intubation

procedure. Subsequent to this adjustment period, four

15 minutes samples are taken.

4. If the basal secretion study is to be followed by the

augmented histamine test, a suitable dose of antihistamine be given parenterally 30 minutes before

completing the collection of basal secretion.

5. For each 15 minutes sample, the volume, pH, and

titrable acidity are measured and the acid output

calculated. The sum of the acid outputs in the 4 samples,

expressed in milliequivalents, represents the 1 hour

basal acid output.

Interpretation

The mean basal acid output reported for normal males

ranges from 1.3 to 4.0 mEq/h. Lower values occur in females

and with ageing. Somewhat lower values are reported in

most large series for gastric carcinoma and benign gastric

428 Concise Book of Medical Laboratory Technology: Methods and Interpretations ulcer and distinctively higher values for duodenal ulcer

or jejunal ulcer following partial gastrectomy with gastrojejunostomy. Extremely high acid output is present in

patients with the Zollinger-Ellison syndrome.

Augmented Histamine Test (AHT)

A dose of 0.04 mg per kg body weight is the optimum

dosage that can be given, and any further increase in

dosage does not increase the gastric acid output. All

parietal cells capable of acid secretion are stimulated by

histamine (functioning parietal cell mass). The AHT or the

analogous Histalog test are now established as definitive

tests for the diagnosis of anacidity.

The side effects of histamine are overcome by previous

administration of antihistamine. A history of bronchial

asthma or urticaria, the presence of severe cardiac,

pulmonary or renal disease and paroxysmal hypertension

or other possible signs and symptoms of pheochromocytoma are contraindications to the performance of this

test.

Method

1. Following a 12 hours fast, basal secretion is collected

for 1 hour as previously described.

2. Thirty minutes before completion of the basal

secretion collection, a suitable dose of antihistamine

is given IM, e.g. 10 mg chlorpheniramine maleate or

50 mg diphenhydramine hydrochloride.

3. After the conclusion of the basal secretion study,

histamine acid phosphate is administered subcutaneously in a dose of 0.04 mg per kg body weight.

4. Gastric contents are then collected in 15 minute

samples for 1 hour.

5. The volume, pH and titrable acidity are measured for

each sample and the acid output is calculated. From

these, the 1 hour or maximal acid output in mEq is

computed.

Interpretation

The maximum rate of acid secretion is characteristically

attained within 15 minutes after histamine injection and is

maintained for approximately 30 minutes. By 60 minutes

after histamine injection, acid secretion usually falls to the

basal level. The maximum output, representing the sum of

the acid.

The upper limit of normal is 30 mEq HCl secreted in the

30 minutes period between 15 and 45 minutes after the

histamine injection. Values higher than the stated upper

normal limit are usually found in duodenal ulcer and

Zollinger-Ellison syndrome. Anacidity in the augmented

histamine test is most commonly found in adults with

pernicious anemia or gastric carcinoma, it has also been

reported in other conditions, e.g. hypochromic anemia,

rheumatoid arthritis, steatorrhea, aplastic anemia,

myxedema, nutritional megaloblastic anemia and the

asymptomatic relatives of patients with pernicious anemia.

The basal and AHT are used as determining factors

for gastrectomy or vagotomy. It has been suggested that

an increased functioning parietal cell mass evidenced by

an elevated maximal acid output indicates the need for

gastric resection. Whereas, raised basal secretion with

normal or only slightly elevated maximal secretion is taken

as an indication for vagotomy.

Histamine Infusion Test

The use of a slow IV infusion of histamine allows

measurement of acid output in a sustained steady state.

Advantages

1. It obviates the need for doing both basal and

augmented histamine tests.

2. The greater acid output achieved in the sustained

steady state facilitates the detection of low levels of

acid output.

3. This is a highly reproducible test.

4. The slow histamine infusion has lesser side effects.

Method

1. The patient is intubated following a 12 hours overnight

fast.

2. A basal hour collection is obtained.

3. Thirty minutes before completion of the basal hour, a

suitable dose of antihistamine is given intramuscularly.

4. After completion of the basal hour, an IV infusion

of histamine in physiologic saline is begun and the

dose rate is adjusted to deliver 0.04 mg of histamine

phosphate per kg body weight per hour.

5. The infusion is continued until four 15 minute steady

state samples have been collected. The initiation of

the steady state is evident from the plateau reached

in volume output and usually requires about 30 to 45

minutes to obtain after the start of the infusion.

6. Each sample of the basal hour and steady state is

analyzed for volume, pH and titrable acidity.

Interpretation

The normal values of acid output in mEq/hour for males is

16 to 32 and for females 18 to 25. The values are markedly

higher in duodenal ulcer patients.

Histalog Test

Histalog (3 β-aminoethyl pyrazole dihydrochloride,

Betazole), an analog of histamine can be used instead of

histamine.

Examination of Gastrointestinal Contents 429

Advantage: Lesser side effects and obviation of the need to

give antihistamine.

The augmented Histalog dosage is 1.7 mg/kg given IM.

The test is similar as AHT except that: (i) no antihistamine

is needed, and (ii) eight instead of four 15 minute postHistalog samples are collected.

The peak acid secretion in Histalog test is reached in the

second to fifth 15-minute period. The peak secretory rate

may last for 45 to 90 minutes.

Insulin Hypoglycemia Test

Acid secretion is stimulated by hypoglycemia caused by

insulin administration. The major stimulus is transmitted

via vagus nerve and can be removed by vagotomy.

Hypoglycemic response—for about 30 minutes after

insulin injection there is a slight depression of gastric

secretion.

The predominant effect during the remainder of the

first 2 hours consists of marked enhancement of gastric

secretion.

The final effect is manifested after 2 hours and is also

stimulatory to gastric secretion (the second phase is via

the vagus and the third is humoral via the adrenocortical

hormones—hence the second but not the third stage can

be abolished by vagotomy).

Method

1. Following a 12 hours overnight fast the patient is

intubated. Two hours basal secretion is obtained in

15 minutes samples.

2. Blood samples for glucose estimation are obtained

upon completion of the basal secretion study and at

30, 60 and 90 minutes after insulin injection.

3. Insulin is given IV either at a fixed dosage of 15 or 20

units or at a calculated dosage of 0.20 units per kg of

body weight (keep a 50 mL syringe filled with 50%-w/vglucose solution readily available to counteract any

serious hypoglycemic effects).

4. Gastric secretion is collected in 15 minute samples for

2 hours after insulin.

5. For each basal and postinsulin gastric sample, the

volume and titrable acidity are determined, and the

acid output is computed.

Interpretation

This test is valid only if the blood glucose falls below

50  mg% at some point of the test, which will usually be

30 minutes after insulin administration. Validity of the test

also depends upon the capability of the stomach to secrete

hydrochloric acid. Hence, if no acid is present in either

the basal or postinsulin periods, it is necessary to perform

an augmented histamine test in an attempt to evoke acid

secretion. If the stomach is truely anacidic, no conclusion

can be drawn regarding the completeness of vagotomy, but

the question of simple peptic ulceration is then effectively

excluded.

The patient can be considered completely vagotomized

if the acid output in the greater of the two postinsulin

hours is less than the greater of the two basal hours.

Incomplete vagotomy is likely if the acid output in the 2

hour postinsulin period exceeds that of the 2 hour basal

period by more than 0.5 mEq. Incomplete vagotomy is

also suggested by an acid output of greater than 2 mEq

in either basal hour. In incomplete vagotomy if acid output is elevated in the first postinsulin hour—the prognosis

is bad in the sense that recurrence may occur; whereas,

elevation in the second hour is less likely to be followed by

a recurrence.

Gastrin Secretory Test

One mg of gastrin (prepared from gastric antrum of Swine)

per kg of body weight can be given subcutaneously or else

a single 50 g IV injection can be given. Most subjects will

show a maximum output beginning about 20 minutes

after gastrin injection and will maintain this level of acid

output for 20 to 40 minutes. The response is quite rapid

with IV administration, with peak levels occurring in 5 to

10 minutes.

Pentagastrin (a synthetic pentapeptide with gastrin

nucleus) can be used instead of gastrin, the results are

reproducible and without the side effects of histamine.

Miscellaneous Investigations

Mycobacterial culture: Individuals having pulmonary

tuberculosis but cannot produce sputum or in children

who cannot effectively expectorate, this method of

aspirating and culturing the gastric contents is quite useful.

It is essential that the gastric contents be collected in the

early morning prior to eating or drinking and preferably

immediately upon awakening before increased gastric

motor activity has largely emptied its contents. The sample

withdrawn should be immediately submitted for culturing.

Exfoliative cytology: For diagnosing gastric carcinomas—

gastric cytology, gastroscopy and roentgenography—

can be used, but the most discriminating information is

provided by exfoliative cytology (chymotrypsin can be

used to facilitate the exfoliation of cells by liquefying the

mucus coating). Diagnosis rate is almost 90%.

430 Concise Book of Medical Laboratory Technology: Methods and Interpretations EXAMINATION OF DUODENAL CONTENTS

Duodenal Drainage

Indications

1. For diagnosis of liver or biliary tract disease. Drainage

may be done to help diagnose exacerbations of chronic

infections early so that they can be controlled.

2. For other diagnostic purposes relating to parasites,

pancreatic enzyme, etc.

3. For therapeutic drainage in cholangitis or biliary

obstruction.

Method for Diagnostic Drainage

1. Give nothing orally after midnight.

2. In the morning intubate (Rehfuss or Levintube)

to a length of 50 cm (29 inches). Withdraw gastric

specimen.

3. With the patient erect or lying on his right side before

the fluoroscope, feed and massage tube into middle

third of the duodenum. Now aspirate duodenal

contents for 5–30 minutes and label “A”, this evacuation

specimen is of little value for bile study.

4. Slowly inject 50 mL of warm 33% magnesium sulfate

through the tube to relax sphincter of Oddi. Clamp

tube for 5 minutes then drain for 30 minutes and label

“B”. Gallbladder bile is first dark, then lighter. If no “B”

bile is obtained, inject another 50 mL of magnesium

sulfate. If still unsuccessful, inject 30 mL of olive oil.

5. During the final period of 30 minutes, try to collect

yellow hepatic bile. Label it “C”.

Examination for Diagnosis

1. Note density, color, and flocculi in all three specimens.

Test for bile, blood, reaction, and ferments as necessary.

2. Microscopy: This is important in detecting early

cholelithiasis (gallsand). Note pus cells, bacteria,

cellular elements and crystals.

3. Giardia or other parasites may be present.

4. Culture for bacteria, especially typhoid bacilli.

Interpretation

1. Absence of dark “B” bile indicates loss of gallbladder

function. No bile may appear in common duct

obstruction.

2. In cholelithiasis, many cholesterol and calcium

bilirubinate crystals appear in “B” and “C” bile. The

cholesterol crystals may be perfect or atypical or

may be mixed with cellular detritus. The calcium

bilirubinate comes as yellow or reddish particles in

the size of a pinhead.

3. In biliary tract inflammation, there is much yellow

cellular and bacterial materials in “B” and “C” bile.

4. Blood may be grossly visible in advanced carcinoma.

COMPOSITION OF BILE

Gross and Chemical Characteristics

a. Volume per 24 hours: 700–1000 mL

b. Specific gravity: Hepatic duct—1.01, gallbladder

—1.026 to 1.032.

c. Total Solids

 Hepatic duct Gallbladder

 (g%) (g%)

• Bile salts 1.8 8.7

• Fatty acids

 and lipids 0.24 1.8

• Cholesterol 0.16 0.87

d. pH : Hepatic duct, 7.5 (6.2–8.5);

 gallbladder, 6.0 (5.6–8.0)

e. Sodium : 134–156 mEq/L

f. Potassium : 3.9–6.3 mEq/L

g. Chloride : 83–110 mEq/L

h. Bicarbonate : 38 mEq/L.

PANCREATIC FUNCTION TESTS

Composition of Pancreatic Juice

Obtain specimen by duodenal drainage, it is mixed with

bile. The flow of pancreatic juice is stimulated by an

injection of secretin. Secretin is a hormone normally

produced by upper intestinal mucosa in response to

the presence of acid. The flow of pancreatic juice begins

5 minutes after a meal, is at its height in 2–3 hours, lasts

6–8 hours in all.

Gross and Chemical Characteristics of Pancreatic Juice

a. Volume per 24 hours: 500–800 mL.

b. Specific gravity: 1.007.

c. Total solids: 1.5–2.5 g%.

d. Alkalinity: pH is 7.0–8.2; 10 mL of pancreatic juice =

10–13 mL of 0.1 N NaOH and is more effective than

bile or succus entericus in neutralizing acidic gastric

juice.

e. Bicarbonate: 70–100 mEq/L.

f. Sodium: 100–150 mEq/L.

g. Potassium: 2–8 mEq/L.

h. Chlorides: 50–95 mEq/L.

Examination of Gastrointestinal Contents 431

Digestive Enzymes

Proteolytic Enzymes

1. Trypsin is a pancreatic protease. There are 100-200

units/L. It is much more active than pepsin. The inactive

trypsinogen secreted is activated by enterokinase or by

trypsin itself. Trypsin hydrolyzes proteins at peptide

bonds.

2. Chymotrypsin: Two forms, A and B are secreted and

are activated by trypsin. Its action is like that of trypsin.

3. Collagenase: It digests collagen and is the one that

initiates tissue destruction in necrotizing pancreatitis.