Clinical chemistry
Clinical chemistry (also known as clinical biochemistry, chemical pathology, medical biochemistry or
pure blood chemistry) is the area of pathology that is generally concerned with analysis of bodily
fluids.
Diabetic Workup
Normal
Serum Glucose (Fasting)
Pathology
70 – 110mg/dL
>126mg/dL (Diabetes Mellitus) Criteria 1
500 – 700 mg/dL (Ketoacidosis)
<50mg/dL (Hypoglycemia)
Random Blood Glucose
OGTT
3 (after taking 75 mg glucose)
<200mg/dL
>200mg/dL
<140mg/dL
HbA1c
Criteria 2
>200mg/dL
<7%
>8%
Criteria
(not diagnostic)
Indicating Diabetic Nephropathy
Urine Albumin
0
>30mg/day (microalbuminuria)
>300mg/day (macroalbuminuria)
Liver Function Tests
1. Hepatocyte Injury
Normal
AST
(10-40 U/L) upto 40 U/L
ALT
(9-60 U/L) upto 40 U/L
LDH
Pathological
2.
Billiary Excretory Function
Serum Billirubin
Total
<1.2mg/dL
Direct
0–0.3 mg/dL
>2.0mg/dL
Indirect
Serum Alkaline Phosphatase
gammaGlutamyl Transpeptidase
(30 – 120 IU/L)upto 70 U/L
0 to 51 IU/L
3. Hepatocyte Function
Serum Albumin
3.9 – 5.0 g/dL
Prothrombin Time
12–15 seconds (raised in chronic liver disease)
INR
0.8–1.2
Serum Ammonia
10-80 ug/dl
Note : AST > ALT ; alcoholic hepatitis
ALT> AST ; viral hepatitis
An increased levels of direct bilirubin and alk. Phosphatase (with normal indirect bilirubin and normal
Hb) is always jaundice secondary to extrahepatic obstruction.
Eg. A 54 year old man presents with high fever, jaundice and colicky abdominal pain in the rt. Upper
quadrant (this is classic Charcot’s triad ). The gall bladder can not be palpated ( this excludes carcinoma
of the head of the pancreas by Courvoisier’s Law) workup reveals Hb 15.3mg/dL, unconjugated bilirubin
level 0.9mg/dL, conjugated bilirubin level of 1.1mg/dL and Alk.phosphatase level of 180 IU/L/ which of
the following is the diagnosis.
a.
b.
c.
d.
e.
Acute cholecystitis
Chronic cholecystitis
Bileduct obstruction by stone
Carcinoma of gallbladder
Carcinoma of the head of pancreas
Jaundice
Jaundice Type
Hepatocellular
Obstructive
Hemolytic
Hyperbilirubinemia
Conjugated/Unconjugated
Conjugated
Unconjugated
Urine Bilirubin
↑
↑
Absent
Urine Urobilinogen
Normal/↓
↓
↑
Enzyme Markers
Serum Enzyme
Diagnostic Use
AST/ALT
Viral Hepatitis, Alcoholic Hepatitis, MI (AST)
GGT
to find whether ALP is raised
elevated even in subclinical liver dysfunction, it is used
In biliary or extrabiliary disease.
ALk.Phosphatase
Obstructive Liver Disease, Bone Mets.
Amylase/Lipase
Acute Pancreatitis
Markers of Viral Hepatitis (raised levels indicate)
(SEQ point of view)
Hepatitis A
IgM anti HAV
indicates new infection
IgG anti HAV
indicates old infection (obtained by Total Anti HAV – IgM anti HAV)
Hepatitis B
HBsAg
HBsAb (anti HBsAg)
HBeAg
indicates infection
indicates immunity
indicates viral activity
HBeAb (anti HBsAg)
peak of infection; indicates waning
IgM anti HBcAg
indicates new infection
IgG anti HBcAg
indicates old infection
(MCQ point of view)
HBsAg
HBeAg
IgM anti HBcAg
IgG anti HBcAg
IgG HBsAb
HBV-DNA
Acute Infection
+
+
Window Period*
+
Previous Infection
+
+
Immunization
+
Chronic Infection
+
+
+
* Window Period is defined as the timeperiod in which the HBsAg disappears and the HBsAb appears.
eg.
A 27 year old man with a history of IV drug use is seen in the emergency department because he has
experienced nausea, vomiting and passage of dark coloured urine for the past week. Physical
examination shows scleral icterus and mild jaundice. There are both recent and healed track marks in
the right antecubital fossa. Neurological exam shows a confused, somnolent man oriented only to
person. He exhibits asterixis. Lab studies show:
Total Protein
5.0g/dL
Albumin
2.7g/dL
AST
2342 U/L
ALT
2150 U/L
Alk.Phos.
233U/L
Total bilirubin
8.3 mg/dL
Direct bilirubin
4.5 mg/dL
HBsAg
Positive
Anti HBs
Negative
Anti-Hbc
positive
Anti-HBc IgM
negative
Anti HAV
negative
Anti HCV
negative
Anti HDV
positive
Which is the likely diagnosis
a. Acute HBV infection
b. Chronic HBV infection
c. Acute HAV infection
d. Acute Co infection of HBV and HDV
e. Superinfection of HBV with HDV
From the clinical picture itself it is obvious that the person has HBV due to IV abuse. Also if you look at
the workup you will find that Anti HBc IgM is negative which means there is previous infection with HBV,
besides Anti HDV is positive too which means the answer is e.). AST>ALT. it cud be b.) but e.) is more
likely. Anti HAV is negative that rules out c.). for acute co-infection anti HBc Ig M shud be positive.
Cardiac Workup (ENZYMES)
Troponin (cTn1)
CPK-MB
LDH 1
SGOT
Increases in
(after chest pain)
(in hours)
4-6
4-8
10-12
Peaks at
(in hours)
12-24
12-24
2-3 days
Wanes in
(in days)
3-10
3-4
7-10
Normal Value NV
(in IU/L)
0-0.1 (ng/mL)
250
230-460
5-40
Examples
1. A 60 year old male presents with acute retrosternal chest pain to the emergency department.
Lab investigations show total CK 360 U/L (NV : upto 195U/L) CK MB 32 U/L, SGOT 54 U/L, LDH
418 U/L. ECG was consistent with Acute MI. What is the possible duration of his present attack?
a. 30 minutes
b. 2 hours
c. 12 hours
d. 36 hours
e. 5 days
Here Total CK is elevated means that there has been atleast greater than 4 hours to the injury,
CK MB is normal (with this u have to look at LDH or SGOT) means that it has peaked nd is now
waning or did not increase in any case it wud peak at 12 hours. Now LDH is elevated and it
increases at 12 hours. So using both these values the answer is c.)
2. A 45 year old male experiences crushing substernal chest pain on arriving at work in the
morning. Over next few hours the pain persists and begins to radiate to his left arm. He
becomes diaphoretic and short of breath, but he waits till the end of his 8 hours shift to go to
the hospital. Which of the following serum lab test finding is most useful to diagnose his
condition on admission to hospital?
a. Elevated lipase
b. Elevated AST
c. Elevated CK-MB
d. Elevated LDH
e. Elevated troponin
Ans. C.)
Note I cud not find times for SGOT(AST), because it is a redundant test and is now no longer
used for cardiac workup. It is replaced by troponin.
Troponin values are measured from a graph based on multiples of cut off values that range from
50-100 during injury.
Myoglobin is a recent marker (10 – 95ng/mL) increases in 1-3 hours peaks at 6-10 hours and
wanes in 12-24 hours.
TUMOUR MARKERS
Prostate Specific Antigen (PSA)
used to screen for Prostate Carcinoma
>1ng/mL Cancer
< 1ng/mL BPH
Prostatic Acid Phosphatase
CarcinoEmbryonicAntigen (CEA)
produced by 70% of colorectal and pancreatic
carcinomas, also by gastric and breast carcinomas
Alpha Fetoprotein
HepatoCellular Carcinoma
Non seminomatous Tumours of the Testis
(Endodermal Sinus Tumour aka Yolk Sac Tumour)
Beta HCG
Hydatidiform Mole, Choriocarcinomas,
Gestational trophoblastic tumours
CA-125
Ovarian Cancer
Alkaline Phosphatase
Mets. To bone, Paget’s disease
Examples.
1. During routine exam of a 70 year old male the prostate is found to be normal in size on
palpation. He has serum PSA 17ng/mL. a routine urinanalysis reveals no abnormalities. He is
healthy with H/O no major illness. Which of the following histologic finding is seen on prostate
biopsy
a. Hyperplastic nodules of the stroma and glands lined by 2 layers
b. Poorly differentiated glands lined by a single layer of epithelium and packed back to back
c. Foci of chronic inflammatory cells in the stroma and in normal appearing glands
d. Areas of liquefactive necrosis
e. Multiple caseating granulomas
Answer. B.) bcos PSA levels indicate cancer.
2. A 70 year old man C/O nocturia, urinary urgency and a feeling that he could not completely
empty his bladder. A digital exam reveals a firm enlarged prostate. Bone scan is ordered and
shows positivity in multiple vertebral bodies. Elevtion of which of the following substances
would be most strongly associated with development of bone lesions.
a. PSA
b. Prostatic acid phosphatase
c. Alk.Phosphatase
d. Tartrate Resistance Acid Phosphatase
e. Urinary hydroxyl proline
Answer. C.) TRAP is elevated in hairy cell leukemia.
Renal Function Tests
Urinalysis
Serum creatine 0.6-1.5 mg/dL
Serum Urea (BUN) 8-25 mg/dL

Increased BUN is, by definition, azotemia. It is due either to increased protein catabolism
or impaired kidney function
Increased protein catabolism results from:
a really big protein meal
severe stress
upper GI bleeding
Impaired kidney function may be "prerenal", "renal", or "postrenal".
Prerenal azotemia results from underperfusion of the kidney:
dehydration, hemorrhage, shock, congestive heart failure
Renal azotemia has several familiar causes:
acute tubular necrosis, chronic interstitial nephritis, some
glomerulonephritis
Postrenal azotemia results from obstruction of urinary flow:
prostate trouble, stones, surgical mishaps, tumors

Decreased BUN
Lack of protein (celiac disease, some patients with nephrotic syndrome)
Severe liver disease (end-stage cirrhosis, yellow atrophy, really bad hepatitis, halothane
or acetaminophen toxicity, enzyme defects)
Overhydration (iatrogenic, psychogenic water-drinking)
Ability to concentrate urine based on hygrometer, refractometer, or dipstick.
Less Significant
Pituitary
Prolactin
Corticotropin
Thyroid Function Tests
2 -30 ng/mL
TSH
0.3 to 3 mIU/ml
T4
4 - 11 mcg/dL
Free T4
0.8 to 1.7 mcg/dl
T3
97 to 219 ng/dl
Free T3
210 to 440 pg/dl
Thyroid binding globulin
Albumin
Iodine Uptake
Diseases
TSH
Primary Thyrotoxicosis
decreased
T3
increased
T4
increased
Secondary Thyrotoxicosis
increased
increased
increased
T3 thyrotoxicosis
undetectable
increased
decreased
Primary Hypothyroidism
increased
decreased
decreased
Hashimoto’s
normal
decreased
Parathyroid
Calcium
8.5 to 10.2 mg/dL
PTH
10-60 pg/ml
Primary Hyperparathyroidism
-inc. PTH, inc. serum Ca2+
Secondary Hyperparathyoidism
-inc.PTH, hypocalcemia with hyperphosphatemia
Adrenal Cortex
ACTH
Cortisol
Exogenous Glucs.
Dec.
inc.
Cushing’s Disease
inc.
inc.
Acute Adrenocort. Insuf..
inc.
dec.
Addison’s
inc.
dec, with hypercalcemia, hypoglycemia,
hyponatremia, hyperkalemia, eosinophila, metabolic acidosis
Secondary Insuf..
By
Muhammad Usman Zafar
4th year MBBS
SIMS
Batch 2005-10
inc.
may respond to ACTH test