Lab and dx test: Chemistry studies

The ability of a test to correctly identify people who do not have the disease

• low false positive = high specificity
• lower false positive = higher false negative

• The probability that the test will be negative
• among people who do not have  the disease. - if test is negative, might need to retest due to the high number of false positive - if test positive - most likely you have the disease.

The ability of a test to correctly identify those individuals who actually have the disease

The probability that the test is positive in a group of patients that have the disease

Fewer false negatives --> Higher risk of false positives

if negative yey!! if positive might need to be retested.

• 1. ELISA - more sensitive ( detect who has the disease, high rate of false positive)
• 2- Western Blot - more specific ( detect who does not have the disease, can help detect false positives)
• 3- if indeterminate - HIV DNA PCR - even more specific.
• Indeterminate = 2 of the 3 specified bands are positive on WB

• Positive: —The probability that a patient who tested positive for the disease actually has
• that disease

• Negative: —The probability that a patient who tested negative for a disease will not
• have the disease

• 135-145
• It is involved in:
• - osmotic pressure
• - acid base balance
• - nerve impulse - esp those regulating the heart.
• Panic level: < 110 - often not r/t dietary intake
• - impaired cognition, dec LOC, convulsions - abdo pain, cramping, oliguria, rapid and weak pulse

—Common: Dehydration, vomiting, diarrhea

• —Medications: Calcium, estrogen, clonidine,
• viagra

—Less common: CHF, Cushing’s, diabetes insipidus, Zollinger-Ellison syndrome

• —Common: diabetes mellitus, hyperglycemia,
• hypothyroidism, vomiting, malnutrition,
• water intoxication

• —Medications: Diuretics, heparin,
• laxative, NSAIDs, SUs

• —Less common: Addison’s, adrenal
• insufficiency, burns, bowel obstruction, cirrhosis, emphysema, hyperthermia,
• cerebral palsy, malabsorption, kidney problems, metabolic acidosis,
• syndrome of inappropriate antidiuretic hormone secretion, CHF (edema)

•Also, high trigycerides and low protein can cause artificially low sodium values

• •Clinical decision making- if sodium
• is high or low think
• 1. Acute illness (vomiting, diarrhea)?
• 2. Chronic disease? (kidneys, CHF) - manage underlying disease.
• 3. Medications (focus on diuretic and seizure medications) - stop med!

3.5 -5

• What does potassium do?
• Cellular water balance
• Electrical conduction in muscle cells
• Cardiac rhythm

Panic level: ≤2.5 mEq/L, ≥6.6 mEq/L

• —High: muscle cramps, diarrhea,
• peaked T waves, v-fib

—Low: Malaise, polyurea, thirst, low BP, depressed T waves, weak pulse

• —Common: Dehydration, cell damage (burns),
• renal failure or obstruction, excessive intake, uncontrolled diabetes, preparation
• errors

• —Meds: Calcium, ACE inhibitors, ARBs,
• estrogen, heparin, potassium sparring diuretics

• —Less common: Addison’s, acidosis,
• hemolytic anemia, shock, thrombocytosis, intestinal obstruction, infection

• —Common: Diarrhea, vomiting, alcoholism,
• anorexia/starvation, medications

• —Meds: Albuterol, ASA, corticosteroids,
• diuretics, insulin

• —Less common: Cerebral palsy, colon
• cancer, Cushings, cirrhosis, CHF, stress, shock, draining wounds

• Clinical decision making:
• 1. Was the patient acutely ill?  ( esp GI)
• 2. Chronic conditions?  ( always check kidney)
• 3. Diet changes?
• 4. Medications? ( HTN meds)

• 95-108 mEq/L
• What does Chloride do?
• - Anion counter balancing sodium
• - Aids in digestion
• - —Maintains osmotic pressure and water balance
• - —Bugger in oxygen/carbon dioxide exchange

• Panic level: ˂ 80 mEq/L or ˃115 mEq/L
• - Hypotension
• - Cardiac dysrhythmias
• - Impaired mental status

—Common: Dehydration, alcoholism, diarrhea, hypernatremia

—Meds: Chlorothiazide, corticosteroids, methyldopa

—Less common: Acidosis, alkalosis, CHF, Cushing’s, diabetes insipidus, hyperparathyroidism, renal disease/failure, eclampsia, fever, salicylate intoxication

• —Common: Burns, diabetic ketoacidosis,
• severe diarrhea, edema, emphysema, fasting, fever, hypokalemia, hyponatremia, medications

• —Meds: Corticosteroids, prednisone,
• diuretics

• —Less Common: Acidosis, ALS, CHF,
• pneumonia, nephritis, water intoxication

• 1. Look at sodium level, ( normal?)
• 2. Consider acute illness/dehyrdation ( think causes of dehydration)
• 3. Check meds
• 4. If sodium and renal function are OK consider rechecking. Also, if the specimen was hemolyzed the results will not be accurate

22-30 mEq/L

• What does CO2 do?
• - Guide to body’s buffering system
• - —Acid-base balance
• - Regulated by the kidneys
• Panic level ˂ 15 mEq/L or ˃ 50 mEq/L

• —Common: Hypoventilation, pneumonia,
• severe vomiting, emphysema

—Meds: Antacids, diuretics (mercurial, thiazide)

• —Less common: Airway obstruction/embolism,
• renal disorders, respiratory acidosis

• —Common: Dehydration, severe diarrhea,
• hyperventilation, lactic acidosis

—Meds: ASA, chorothiazide diuretics, nitrofurantoin, tetracycline 

• —Less common: Alcoholic ketosis, diabetic
• ketoacidosis, renal disorders/failure, starvation, salicylate intoxication

• 1. The conditions of the blood draw often affect the results. ( If patients are very nervous they may hyperventilate elevating the CO2 level,
• fist pumping for a hard draw will also elevate the results)
• 2. Think about lungs problems (if significant change)
• 3. severe GI problems 
• 4. kidney function.  
• 5. Review med list

60-98 mg/dL --> Diabetes is diagnosed as fasting ≥ 126 or non-fasting ≥ 200.

• What does glucose do?
• - Formed from digestion of carbs and conversion of glycogen
• - —Body’s energy level

Panic level: <40 mg/dL or ˃ 700 mg/dL ( 500 to 700)

—Common: Diabetes mellitus, acute stress, medications

—Meds: Steroids, APA, atenolol, diuretics, indomethacin, niacin, thyroid medications

• —Less common: Cushings, pancreatitis, pheochromocytoma, pituitary ademona,
• renal disease, vit B deficiency, renal disease, cystic fibrosis

• —Common: insulin overdose, diabetic
• medications

—Meds: Tylenol, beta blockers, insulin, oral hypoglycemic agents 

• Less common: pancreatic islet cell carcinoma, liver damage, liver damage, hyperinsulemia,
• hypopituitarism, hypothyroidism

• Start workup for diabetes
• Consider medications
• Endocrinology

• Normal range:
• 5-21

• What is BUN?
• —Formed by the liver through an enzymatic protein-breakdown process
• —Filtered through the renal glomeruli

• Panic levels: ˃100 mg/dL = kidneys are not functioning
• Agitation, confusion, nausea and
• vomiting, acidemia

—Common: Dehydration, urinary tract obstruction, blood loss from GI tract, excessive protein intake, kidney disease


—Meds: ACE inhibitors, clonidine, lasix, naprocen, sulfonylureas, thiazide diuretics, antibiotics

• —Less common: CHF, ketoacidosis,
• shock, MI, gout, sickle cell anemia, lupus , scleroderma, medications

• —Low protein, high carb diet,
• malnutrition, pregnancy, acromegally, celiac disease, cirrhosis, liver disease

• 1.Evaluate the kidneys- always interpret with creatinine and compare over time.
• 2. Make sure you’ve got a recent hemoglobin and negative guaiac. - check for anemia.
• 3. Consider anything limiting kidney profusion.( stone, HF, obstruction)
• 4. Look at diet ( low protein) and medications

- #1 indicator of kidney function.

• —Men: 0.6-1.2 mg/dL
• —Women: 0.5-1.1 mg/dL

What is creatinine?

• —- End product of skeletal muscle metabolism
• - —Constantly excreted by kidneys
• - —Indictor of renal function (GFR)

• Never evaluate creatinine by normal range alone
• --> Always interpret over time --> A value can be in normal range and
• represent a big problem

• —Renal disease, diabetes, CHF (kidneys not getting enough blood), gout,
• hypothyroidism, muscle destruction, preeclampsia, RA, sickle cell anemia  

• —Meds: Acyclovir, ACE inhibitors,
• diuretics, ARBs, sulfonamides, testosterone

• —Falsely elevated by excessive exercise
• and red meat, 20-40% higher in late afternoon, medication often elevate

• —Diabetic ketoacidosis, muscular
• dystrophy, anemia, leukemia, medications

—Meds: Thiazide diuretics, cimetidine

• 1- Compare w/ previous levels
• 2- Consider GFR, BUN, and potassium
• 3- Acute bc chronic kidney disease ( ask: what additional info do I need to determine if kidney damage is acute or chronic?)

GFR is the sum of the filtration rates in all functioning nephrons

Normal GFR is ˃60

Stages of Chronic Kidney Disease 

• 1 - Kidney damage with normal or increased GFR
• ≥90
• 2-Kidney damage with mild decrease - 60-89

3- Moderate decrease in GFR - 30-59

4 - Severe decrease in GFR - 15-29

5 - Kidney Failure  ˂15 or dialysis

Don't wait too late before making the referral to the neuphrologist. - stage 3-4 too late.

• —- Clinical follow up with dietary instruction and clinical management every 6 months
• - CVD risk: exercise, smoking cessation, lipid control
• - —Control of calcium, phosphorus, PTH
• - Manage anemia (goal 11-12g)
• - —HepB immunization
• - ACE or ARB
• - —Assessment for transplant/functioning
• fistula

6.0-8.0 g/dL

• What does total protein mean?
• - —Amount of albumin and globulins in the
• serum
• - —Regulates osmotic pressure
• - —Makes up coagulation factors, hormone,
• enzymes
• - —pH buffers
• - —Tissue growth, repair, transport blood
• components

• —Common: Chronic infection, Dehydration,
• diarrhea/vomiting, liver disease, renal disease ( bc protein isn't being broken down)

• —Meds: Steroids, growth hormone, insulin,
• heparin, levothyroxine

• —Less common: Amyloidosis, autoimmune
• collagen disorders, Crohn’s

• —Common: CHF, hyperthyroidism, liver
• disease, malnutrition or malabsorption, pregnancy

—Meds: Oral contraceptives, salicylates

• —Less Common: Acute cholecystitis, burns, cirrhosis, hemorrhage,
• ulcerative colitis

• 1- Was pt acutely ill? ( d/v)
• 2- Uncontrolled or worsening chronic condition? ( known kidney or liver disease, thyroid disorders, HF?)
• 3- check HIV - if you cannot find the source of protein abnormality.
• 4- consider meds - oral contraceptives, steroids, growth hormones?

• 3.5 g/dL – 5.0 g/dL
• Older adults (3.4 – 4.8 g/dL)

What is albumin?

• —One of two main blood proteins
• —Important in maintaining osmotic pressure
• —Transport protein

• —Common: Dehydration, diarrhea/vomiting,
• renal disease, pregnancy 

• —Meds: Cytotoxic agents, oral
• contraceptives

• —Less common: neoplasms, RA, sarcoidosis,
• lupus, TB, pneumonia, ulcerative colitis, peptic ulcer, Hodgkins’
• Sudden increase = may be caused by cancer.

• —Common: Alcoholism, infection, diabetes,
• hepatitis, hyperthyroidism, malnutrition, stress, trauma 

—Meds: ASA, ampicillin, bacitracin

• —Less common: Fractures, CHF, CF, Crohn’s,
• MI, neoplasms (multiple myeloma), peptic ulcer, lupus, pneumonia, TB, poisoning
• (lead, mercury)

• 1. Is there an acute infection?
• 2. Consider nutritional status: severe
• dehydration, eating disorder, malnourished, chronic illness?
• 3. Consider meds?
• 4. Further testing- always keep
• cancer in mind (retest sooner rather than later)

0.2-1.5 mg/dL (age 1 month to adult)

What does bilirubin indicate?

• —- Breakdown of hemoglobin in red cells
• - Excreted by the liver

Panic level ˃12 mg/dl

• —Conditions causing destruction of red
• blood cells: pernicious anemia, sickle cell, transfusion reactions, hemorrhage,

• Conditions compromising the liver’s
• ability to excrete: hepatitis, cirrhosis, mono, alcoholism, biliary obstruction

—Increased direct bili: cancer of head of pancreas, biliary obstruction, hepatitis, Dubin-Johnson syndrome

Increased indirect bili: hemolytic anemia, soft-tissue hemorrhage (hematoma), MI

• —Other: prolonged fasting, meds: Tylenol, Acyclovir, ASA, antibiotics, ACE inhibitors, iron, warfarin
• Gilbert - for people who are fasting, bili inc.

Phototherapy, caffeine, some medications (penicillin, sulfanomides, corticosteroids )

• 1.Consider liver function: Does patient have known liver disease? Symptoms
• consistent with obstruction?( coming from galbladder stone?
• 2. Consider anemia or recent trauma?
• 3. Consider repeating non-fasting and obtaining indirect and direct to help better differentiate

• 39-117 mU/mL
• —Levels are age and gender specific ( Levels
• are higher in elderly, children, puberty , pregnancy, and females )

• What is Alk Phos?
• Alk Phos is an enzyme found in the liver, bone, intestine and placenta. Can be divided into bone, liver, placental, biliary and intestinal isoenzymes.

—Liver disease: biliary obstruction, space-occupying lesions, cirrhosis, hepatitis, mono, diabetes

• —Bone Disease: Paget’s, metastatic bone
• tumor, osteogenic carcinoma, osteomalacia, RA

• —Other: Hyperparathyroidism, MI, Hodkin’s,
• lung cancer, pancreatic cancer, ulcerative colitis, sarcoidosis, CKD, medications, alcoholism, large carb ingestion, lymphoma, multiple myeloma

—Meds: Tylenol, allopurinol, amitriptyline, COCs, allopurinol, antibitics, colchicine, naproxen, indomethacin, thyroid hormone replacement.

• —Pernicious anemia, celiac disease, hypothyroidism, chronic nephritis
• Osteoporosis does not elevate alk phos
• —Meds: Fluorides, oxalates, phosphates,
• propranolol

•Rule out the obvious: pregnancy, growth spurts, diabetes

•Consider liver problems: check LFTs, bilirubin, hepatitis screen 

•Consider bone etiology: risk factors?

•Retest: Repeat fasting, fractionate

• 10-60 U/L
• What is ALT?

• - Enzyme found in high concentrations in the liver
• - Smaller amounts in heart, muscle, and kidney
• - Catalyst in amino acid production
• - —Very specific to liver
• - Slightly higher in males and black persons

• —Originating in liver: hepatocellular
• disease, liver tumor, cirrhosis, mono, hepatitis, biliary obstruction,

• —Other causes: pancreatitis, MI, severe
• burns, muscle trauma, brain tumor, CVA, hyperglycemia, rhabdomylosis

• —Meds: Allopurinol, antibiotics, ACE
• inhibitors, heparin

—Genitourinary tract infection, malnutrition, steatosis in clients with hep C and weight loss

• 1.Always interpret with AST,
• 2. Think liver- ALT is very specific to liver
• 3.Consider hepatitis screening and ultrasound

5-40 U/L

What is AST?

• —- Found in tissues with high metabolic activity
• - Includes: Heart, liver, skeletal muscles,
• kidney, brain, pancreas, spleen, and lungs
• - Released during tissue death or iNjury

• —MI: increases to 4-10 times normal value,
• peaking at 24 hrs and returning to normal day 4 post- MI

• —Liver disease: hepatitis, cirrhosis,
• mono, cancer, alcoholic hepatitis, Reye’s dyndrome

—Other: brain trauma, polymyositis, pancreatitis, muscle trauma or dystrophy, gangrene, CHF, heat stroke, diabetes

—Meds: Allopurinol, ASA, codeine, antibiotics, thyroid meds

• —Diabetic ketoacidosis, azotemia, chronic
• renal disease, medications
• —May be falsely decreased in severe liver disease
• —Meds: Metronidazole

• 1. Rule out MI (hopefully you did this before the patient left the office)
• 2. Interpret with ALT, if both are elevated start checking the liver.
• 3. Access alcohol use,
• 4. consider musculoskeletal system if no liver cause