Diagnostic Methods (Voiler) Flashcards
Advice:
Work on pattern recognition
Diagnostic tests ahead:
CBC, ELISA, Western blot, urinalysis, blood culture, CSF, microscopy
Chest radiograph:
Pneumonia
Bacterial/Viral/Inflammatory
Pneumothorax
Pleural effusion
Rib fracture
Chest Mass
Lactic Acid
Procalcitonin
Note:
Should not generally see stem cells in the blood stream
CBC
WBC (4.5-11)
Differential:
Basophils, Eosinophils, lymphocytes, monocytes, neutrophils, hemoglobin, hematocrit, MCV, Platelets
emphasis on neutrophils aka left shift=acute infection
Acute phase reactant
platelet count can rise in times of high stress
WBC concepts
Elevation in WBC (Leukocytosis):
-Bacterial Infection
-Leukemia/ blood cancers
-Steroid effect
-Clostridium Diff Infection (taking antibiotics, good bacteria are killed, Cdiff spore releases toxins causing severe diarrhea)
-Recent stressors- surgery/major illness/ MI (myocardial infarction)
Low WBC:(Leukopenia)
-Immunomodulator drugs
-Chemotherapy
-Bone marrow failure
ANC (absolute neutrophil count)
Follow in immunocompromised (ex. myelosuppressive chemo patient, treatment prevent RBC production in bone marrow)
Neutropenia = ANC<1500
-mild 1000-1500
-mod 500-999
-severe<500
opportunistic infection risk
neutropenic fever: life threatening, high mortality
Peripheral blood smear
RBC size/shape
-Hypochromic/normochromic- MCHC -> IDA
-Megaloblastic -> defective DNA-> folate/b12 deficiency
Immunoassay
ELISA most common kind
FIA another common
Add Reagent Antibody (Ab)#enzyme combo specific for target Antigen (Ag) under investigation
Can test for food contamination, environmental, HIV, various uses (not that clinically relevant except for HIV)
Note
Don’t worry too much about how and why this stuff works, mostly focus on diagnostic relevance (when to test people? why? what are you looking for?)
urinalysis:
bacteria showing up might not mean infection, just colonization, in which case you may not need to use antibiotics!
UTI: nitrite in urine is a metabolic product of bacteria (nitrate converted to nitrite)
note:
Sometimes she will start with a broad spectrum “big gun” antibiotic and then get more narrow as results come in so she doesn’t kill off good bacteria
“Pearl, write this down”
When you see someone breathing very quickly, think sepsis as a possibility! This happens when turning into sepsis
ELISA/EIA
Antibody linked enzyme specific for Antigen
Detects Antigen (viral/bacteria) or antibody in blood
Sensitivity usually high,
Used for screening
Enzyme triggered color change
HIV, Lyme disease, COVID, pernicious anemia, RMSF, Syphilis, Allergies, Drugs, Pregnancy
Not great for determining acute vs chronic
FEIA
Measures compounds, drugs, hormones, proteins
Identifies Ab, Ag quantification,-viral particles
Differs in read out from ELISA
common with allergy testing
Western Blot/Immunoblot
Detects microbial Ab to organism (or proteins) in serum/body fluids w/ target antigens (viral)
Detects IgM (1-2week)/IgG (2-6 week) antibodies
Good sensitivity, less than ELISA
Helps exclude false positive ELISA’s as Highly specific
Shiga toxin, HIV, HSV2, Hep B
Cryptococcus, Lyme disease
Influenza
Can have false positives
HIV testing
Subtype 1- common in US
Subtype 2-Western Africa
Indication: Clinical signs (mono or flu like symptoms) / and or high risk exposure
Consideration- if no risk factors- consider screening all 13-75 y/o at least once, all pregnant women
Takes 2 weeks- 6 months to develop antibodies
Sensitivity ~99% >12 weeks post infection
ELISA then if + Western blot to confirm
HIV testing
Subtype 1- common in US
Subtype 2-Western Africa
Indication: Clinical signs (mono or flu like symptoms) / and or high risk exposure
Consideration- if no risk factors- consider screening all 13-75 y/o at least once, all pregnant women
Takes 2 weeks- 6 months to develop antibodies
Sensitivity ~99% >12 weeks post infection
ELISA then if + Western blot to confirm
4th generation ELISA
Combination Ag and Ab testing better detecting acute/early infection, compared w/ Ab only test
HIV testing
CD4 (Helper T cells)-
800-1050 c/mL- normal
<200c/ml = AIDS
Helps staging/risk analysis
CD4 cell count, CD4 count %, HIV RNA, HIV genotype testing
Prophylactic therapy- prevent opportunistic infection (Pneumocystis)- CD4 <200c/mL
Urinalysis
Infection symptoms
-Dysuria/frequency/urgency/bladder pain/lower abdominal pain/
-Flank pain/fevers- kidney infection sx
-Elderly confusion
UTI 2nd most common dx infection
Eval for:
-Hematuria bloody urine)
-Kidney failure
-Diabetes damage- protein
Urinalysis
Infection symptoms
-Dysuria/frequency/urgency/bladder pain/lower abdominal pain/
-Flank pain/fevers- kidney infection sx
-Elderly confusion
UTI 2nd most common dx infection
Eval for:
-Hematuria bloody urine)
-Kidney failure
-Diabetes damage- protein
Urinalysis Indications
hematuria or pyuria
renal disease
abnormalities of ureter
TB in urinary tract
prior to urinary tract surgery
flank pain
in children: polycystic kidney diseases
etc.
Note
Urinalysis details slide 20
Obtaining urinalysis technique:
Clean urethra with wipe
clean catch (mid stream)
UA: microscopic
Eval for
Wbc
Rbc
Bacteria
Crystals
casts (?)
Casts- renal origin, stress, damage, hyaline sometimes normal, glomerulonephritis, kidney injury, nephrotic syndrome
Urine obtained vis clean catch:
incubated on a petri dish, reveals bacterial infection growth if present
Indications for Urinalysis
Pregnant women (doesn’t need sx)
Post menopausal women
Men
Prepubertal children
Urinary tract abnormality
Immunosuppressed
Concern for pyelonephritis
Recurrent UTI’s
Blood Culture and Sensitivity
Indication: Concern for Blood infection
Fevers >100.4
Risk factors for blood infection
Kidney infection
Rigor Chills- very sensitive for blood infection
Signs: tachycardia, Confusion, low bp,
Immunocompromised
IV drug abuser
Prosthetic heart valves
Concern for localized infection spread
Sepsis
Hypotension
Rapid breathing/ heart rate
Indwelling central lines
Foreign bodies
Note:
many helpful resources on this powerpoint, maybe worth saving? (ex. imaging slide)
Aseptic technique
prep skin, vein or line draw, obtain at separate sites, petri dish
CSF analysis
Indication: Concern for Meningitis/Encephalitis , Inflammatory Condition
Infection concern- Headache/Fever/Meningismus- stiff neck
Obtained via lumbar puncture (LP):
Evaluate for intracranial pressure prior
Get CT head first
Contraindicated if:
Infected skin at puncture site
Bleeding issues, csf blockage concern like tumor
Normal values: clear/colorless- yellow tinged think infectio
Lumbar Puncture
Infection patterns
Bacterial Meningitis-
H.Flu kids, Neisseria Meningititis/Strep Pneumonia Adults
Leukocytes/PMN’s elevated
Protein elevated
Glucose low
Gram stain >10^5 CFU
Viral meningitis
Mixed PMN’s/Lymphocytes
Protein elevated
Glucose normal
Check enterovirus/herpes/west nile PCR’s
TB meningitis
Mixed wbc’s,
Protein elevated
Glucose low
AFB staining +
Mycobacterium cx elevated
Fungal Meningitis
Elevated lymphocytes, decreased glucose, elevated protein
Microscopy
Wet prep/mount-microscopic eval
Vaginitis symptoms-itching/burning/rash/odor/discharge
Evals for Yeast, trichomonas, bacterial vaginosis
Tested by:
Wet mount- visual
Potassium hydroxide (KOH) slide-
Evals yeast
Whiff test
KOH, strong fishy odor= bacterial vaginosis
Caveat - Does not eval for all STI’s
good note:
if you hear it a lot, it’s important
Microscopy: stool
Protozoa:
Developing countries
Cyclical sheading- need multiple samples
Microscopy not as reliable as ELISA
Sx: abdominal pain, diarrhea, fever, anorexia, nausea
Recent travel out of country/hiking
Giardia- flagella, Cryptosporidium-small acid fast stain, Entamoeba histolytica
Microscopy Stool indications
Indications: eosinophilia, known exposure, malabsorption, rectal pruitis, most asymptomatic
abdominal pain/nausea/vomiting rare- if large worm burden
Diarrhea/Colitis- more common bacterial/viral/ protozoa infections
Enterotoxic ecoli, Yersenia, Camppylobacter, Shigella, Samonella, Protazoa infection
Helminthic Infections- usually don’t cause diarrhea
Common- Enterobius pin worm (most common US)/ whip worm- mostly asymptomatic
Pin worm- scotch tape test
wet mount, stain
Microscopy stool
Ova &Parasite Eval
Most acute diarrhea causes are infectious-likely viral
Diarrhea usually transient
Indication: Fever, bloody or mucousy stool, profuse watery diarrhea, HIV, enteric bacteremia
Exposure- food, occupation, travel, camping, pets, close contact w/ sick person
Rapid antigen testing-bacterial infections
Chest Radiograph
PA vs AP view
Black= empty
White=increased density
Make sure to review this powerpoint rather than just notecards
the images are helpful plus extra info
Viral pneumonia
Viruses are estimated to cause 30 to 50 percent of CAP cases
Viral pneumonia
Viruses are estimated to cause 30 to 50 percent of CAP cases
Lactic Acid: sepsis marker
represents the anaerobic breakdown of glucose
Big player in Early goal directed therapy w/ Sepsis
Trend mirrors response to treatments
Most common cause of Metabolic Acidosis
Production exceeds clearance
Primary cleared by liver, alittle kidneys, tiny from muscles
Indication: Consider if hypotensive, severe infection, metabolic acidosis w/o obvious cause
Procalcitonin
Biomarker helps distinguish bacterial infections from other infections/inflammation
Goal- reduce antibiotic use
Use as a tool but not your only data point
Not all bacterial infection cause procal to rise
-Atypical not as likely to rise
-Has False positive/false negatives
Guides early antibiotic discontinuation
Chronic kidney have higher baseline levels
