Lab and dx test: Chemistry studies
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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.
How do you test for HIV?
- 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
Predictive values? Pos and neg?
- 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
Sodium : range? What does it do? Panic Range? and what happens at that point?
- 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
SS of Hypernatremia? ( Common causes, meds and less common medical conditions r/t it)
: Dehydration, vomiting, diarrhea
- Medications: Calcium, estrogen, clonidine,
: 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
Critically thinking about sodium levels.
- •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!
Potassium : range? What does it do? Panic Range? and what happens at that point?
- What does potassium do?
- Cellular water balance
- Electrical conduction in muscle cells
- Cardiac rhythm
: ≤2.5 mEq/L, ≥6.6 mEq/L
- High: muscle cramps, diarrhea,
- peaked T waves, v-fib
: Malaise, polyurea, thirst, low BP, depressed T waves, weak pulse
Common, uncommon causes and meds that lead to hyperkalemia?
- Common: Dehydration, cell damage (burns),
- renal failure or obstruction, excessive intake, uncontrolled diabetes, preparation
- Meds: Calcium, ACE inhibitors, ARBs,
- estrogen, heparin, potassium sparring diuretics
- Less common: Addison’s, acidosis,
- hemolytic anemia, shock, thrombocytosis, intestinal obstruction, infection
Common, uncommon causes and meds that lead to hypokalemia?
- 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
Critically thinking about potassium levels.
- Clinical decision making:
- 1. Was the patient acutely ill? ( esp GI)
- 2. Chronic conditions? ( always check kidney)
- 3. Diet changes?
- 4. Medications? ( HTN meds)
Cl level, what does it do? Panic level? and what causes it?
- 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, uncommon causes and meds that lead to high levels of chloride?
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, uncommon causes and meds that lead to low levels of chloride?
- Common: Burns, diabetic ketoacidosis,
- severe diarrhea, edema, emphysema, fasting, fever, hypokalemia, hyponatremia, medications
- Meds: Corticosteroids, prednisone,
- Less Common: Acidosis, ALS, CHF,
- pneumonia, nephritis, water intoxication
Clinical decision making when it comes to not normal chloride levels?
- 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
CO2 normal range? what does it do? panic level? Regulated by what?
- 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
Increased level of CO2?
- Common: Hypoventilation, pneumonia,
- severe vomiting, emphysema
: Antacids, diuretics (mercurial, thiazide)
- Less common: Airway obstruction/embolism,
- renal disorders, respiratory acidosis
Decreased levels of CO2
- Common: Dehydration, severe diarrhea,
- hyperventilation, lactic acidosis
: ASA, chorothiazide diuretics, nitrofurantoin, tetracycline
- Less common: Alcoholic ketosis, diabetic
- ketoacidosis, renal disorders/failure, starvation, salicylate intoxication
Clinical decision making when it comes to CO2 levels:
- 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
Glucose? level? function and panic level?
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
: <40 mg/dL or ˃ 700 mg/dL ( 500 to 700)
: Diabetes mellitus, acute stress, medications
: 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
: Tylenol, beta blockers, insulin, oral hypoglycemic agents
- Less common: pancreatic islet cell carcinoma, liver damage, liver damage, hyperinsulemia,
- hypopituitarism, hypothyroidism
Critical thinking for glucose
- Start workup for diabetes
- Consider medications
- 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
, urinary tract obstruction, blood loss from GI tract
, excessive protein intake
, kidney disease
: 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
Critical thinking for BUN
- 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
: Thiazide diuretics, cimetidine
Critical thinking through Creatinine
- 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
- 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.
Treatment guidelines for Kidney disease
- - 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
- What does total protein mean?
- - Amount of albumin and globulins in the
- - Regulates osmotic pressure
- - Makes up coagulation factors, hormone,
- - pH buffers
- - Tissue growth, repair, transport blood
Increased level of protein
- 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
Low protein levels?
- Common: CHF, hyperthyroidism, liver
- disease, malnutrition or malabsorption, pregnancy
: Oral contraceptives, salicylates
- Less Common: Acute cholecystitis, burns, cirrhosis, hemorrhage,
- ulcerative colitis
Critical thinking through abnormal levels of protein?
- 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?
What is albumin?
- 3.5 g/dL – 5.0 g/dL
- Older adults (3.4 – 4.8 g/dL)
- One of two main blood proteins
- Important in maintaining osmotic pressure
- Transport protein
- Common: Dehydration, diarrhea/vomiting,
- renal disease, pregnancy
- Meds: Cytotoxic agents, oral
- 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
: ASA, ampicillin, bacitracin
- Less common: Fractures, CHF, CF, Crohn’s,
- MI, neoplasms (multiple myeloma), peptic ulcer, lupus, pneumonia, TB, poisoning
- (lead, mercury)
Critical thinking for abnormal albumin level?
- 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
- Conditions causing destruction of red
- blood cells: pernicious anemia, sickle cell, transfusion reactions, hemorrhage,
Increased direct bili
- Conditions compromising the liver’s
- ability to excrete: hepatitis, cirrhosis, mono, alcoholism, biliary obstruction
: 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 )
Critical thinking through abnormal level of bilirubin
- 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.
Inc Alk Phos?
: 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
: Tylenol, allopurinol, amitriptyline, COCs, allopurinol, antibitics, colchicine, naproxen, indomethacin, thyroid hormone replacement.
Dec alk phos?
- Pernicious anemia, celiac disease, hypothyroidism, chronic nephritis
- Osteoporosis does not elevate alk phos
- Meds: Fluorides, oxalates, phosphates,
Critical thinking through Alk Phos?
•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
- - 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
DEC of ALT
Genitourinary tract infection, malnutrition, steatosis in clients with hep C and weight loss
Clinical decision making - ALT
- 1.Always interpret with AST,
- 2. Think liver- ALT is very specific to liver
- 3.Consider hepatitis screening and ultrasound
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
dec AST ( FALSE)
- Diabetic ketoacidosis, azotemia, chronic
- renal disease, medications
- May be falsely decreased in severe liver disease
- Meds: Metronidazole
Clinical decision making - AST
- 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
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