Transcript Laboratory Testing: Its Role in Diagnosing and Managing

LABORATORY TESTING
IN
PRIMARY CARE
OPTOMETRY
Tammy P. Than, MS, OD, FAAO
Carl Vinson VAMC
Dublin, GA
[email protected]
Microbiology
Cultures and Sensitivities
• Mandatory
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central corneal ulcers
hyperacute conjunctivitis
ophthalmia neonatorum
membranous conjunctivitis
Parinaud’s oculoglandular syndrome
postoperative infections
• Recommended
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chronic conjunctivitis
unresponsive conjunctivitis
new practitioner
Cultures and Sensitivities
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specimen preparation is important
no anesthetic – if possible
sterile swab  plate onto culture media
culturette
media:
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Thioglycolate broth
Blood agar
Chocolate agar
Saboraud’s agar
Transport Media
• Amies media without charcoal
Higher yield than other media
 Comparable to plates
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In-Office Microbiology
• Gram Stain
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Gram (+) = purple
Gram (-) = pink
look at morphology
• Cytology
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PMNs = bacterial
lymphocytes = viral
eosinophils = allergic
Diagnostic Imaging
• plain film X-Ray
• CT scan
• MRI
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75 million in 2003
Ultrasonography
Angiography
GDx, OCT, HRT
etc…
Resources
• Imaging of the Globe and Orbit: A Guide
to Differential Diagnosis
Hosten and Bornfield
 Publisher Thieme
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• http://www.med.harvard.edu/AANLIB/h
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ome.html
http://www.loni.ucla.edu/index.shtml
X-Ray: The Basics
• Incident X-Ray enters tissue
• Beam is attenuated
• Exit X-Ray leaves tissue exposes film
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White areas = not exposed
Dark areas = film exposed
3-D represented by 2-D
Black = air (no attenuation)
White = bone
Gray = soft tissue
X-Ray: Types of Views
• Skull / Sinus Series
Caldwell
 Lateral
 Waters
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• Chest
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AP, PA, lateral
• Spinal
CALDWELL
CALDWELL
LATERAL
LATERAL
WATERS
WATERS
X-Ray Indications
• Confirm the integrity of the orbit
Intraocular Foreign Body
 Intraorbital Foreign Body
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• Trauma
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muscle entrapment?
X-Ray Indications
• Sinusitis
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R/O Orbital cellulitis
Horner’s syndrome
Uveitis
Ankylosing spondylitis
Reiter’s syndrome
X-Ray: Contraindications
• Pregnancy
• Excessive Radiation Exposure
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Rad = unit of absorbed energy in tissue
Gray (Gy) = 100 Rad
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the “latest” unit
1 Gy = 100 cGy
chest X-Ray is < 1 cGy
cancer treatment may be 6000 cGy
lens is most sensitive
X-Rays
• Pros
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Inexpensive
Readily available
Rapid results
• Cons
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Radiation exposure
No information about soft tissue
2-D interpretation can be difficult
Case #1
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17 YOM
Hit in eye x 1 day
+ pain
+diplopia
Work-Up
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EOMs
Exophthalmometry
Crepitus?
Nerve sensation
IOP
Imaging
Management
• Nasal decongestants
• Oral antibiotics
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broad spectrum
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e.g. Keflex 500 mg qid
• Don’t blow nose!
• +/- Sx in 1-2 weeks
Other Considerations…
• R/O Seidel’s sign
• Anterior Segment Pathology
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uveitis
corneal abrasion
subconjunctival hemorrhage
• Commotio Retinae
CT Scan: The Basics
• Series of thin X-Ray sections
flat panel detectors may eliminate slices
Emitted X-Rays
Diode sensors
Computer reconstructs views
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CT Scan: The Basics
• CT Numbers
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density < water = negative CT#
density > water = positive CT#
• “Windowing”
• Gray Scale
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White = bone
Black = air
Gray = brain
CT Scan
• Views
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coronal
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sagittal
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paranasal sinuses, orbital integrity
chiasmal pathology
axial
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orbital and visual pathways
CT – The Exam
• Specific protocols
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orbital
chiasmal
brain
sinuses
• Slice thickness and slice increment
• Cranial
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~1 cm / no overlap
• Orbital and Chiasmal
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3 mm with 2 mm between
allows overlap
• Gantry
• 10-20 minutes / scan
Contrast
• Iodine
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good agent for photoelectric capture
enhances visibility of vascular lesions
Administered IV (or intrathecal)
1:40,000 incident of AE
BUN and Creatinine
NPO
Good medication hx
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d/c Metformin (Glucophage) prior to procedure
• CI is shellfish allergy
BUN (Blood Urea Nitrogen)
• actually performed on serum or plasma
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12% higher than blood
• nitrogen portion of urea
• urea is formed in liver from protein breakdown
• filtered through renal glomeruli
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small amount reabsorbed in the tubules
remainder excreted in urine
• azotemia – elevated BUN
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nonspecific
prerenal, renal, or postrenal
BUN (Blood Urea Nitrogen)
• must be compared over time or evaluated with
other tests
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renal function – also assess creatinine levels
fasting not required
Adult 5-20 mg/dL
>60 8-21 mg/dL
increased BUN
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many conditions and many drugs
• decreased BUN
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alcohol abuse, diet lacking protein, liver
destruction, late pregnancy
CREATININE
• product of anaerobic energy-producing
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creatine-phosphate metabolism in skeletal
muscle
excreted by kidneys
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increased levels indicative of decreased glomerular
filtration rate
• Avoid excessive exercise for 8 hours and avoid
excessive red meat for 24 hours before testing
CREATININE
• Normal
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females 0.5 – 1.1 mg/dL
males 0.6 –1.2 mg/dL
elderly – may be lower
• Creatinine clearance, urine
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24 hour collection
• Creatinine clearance, serum urine
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6, 12, or 24 hour collection
blood sample collected anytime during urine
collection period
CT Scan: Artifacts
• Motion
• Dental Fillings
• Partial volume phenomenon
CT Indications
• bone imaging
• calcification
• blood detection
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acute
• meningiomas
• when MRI contraindicated
CT Contraindications
• pregnancy
• excessive radiation exposure
• contrast contraindication
iodine sensitivity
 shellfish allergy
 kidney disease
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CT Scan
• Pros
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High diagnostic yield
Good for bone
Can reconstruct different views
• Cons
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Expensive
Human risk
Motion artifacts
Hard to ddx tumors
MRI
Unpaired protons (H) = tiny magnets
from water and fat
 body is 63% hydrogen atoms
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• Disrupt with radio pulse
• Protons return to original state
• Release energy -> MRI
MRI
• Signal strength: proton density
• Relaxation time: surrounding tissue
• T1 weighted
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Proton density
tissue composition
• T2 weighted
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Tissue differences
• Intermediate
• fat suppression
MRI
• White Matter and Fat
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T1 = bright
T2 = dark
• Gray Matter and CSF
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T1 = dark
T2 = bright
• Vitreous
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T1 = dark
T2 = bright
• blood, air = black
• EOMs and optic nerves = intermediate density
MRI: The Examination
• Gantry
• Flux
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0.5 – 1.5 Tesla
Energy detected
Image reconstructed
40 minutes
+/- gadolinium contrast
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paramagnetic
highlights images of similar density
MRI Indications
• tumors
posterior visual pathway
 brain stem
 pituitary
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• infarcts
• posterior fossa
• MS
MRI Indications
• elevated optic nerve head(s)
• unilateral proptosis
• field loss
hemianopia
 bitemporal
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• cranial nerve palsies
MRI Contraindications
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pregnancy
metallic FB
pacemakers
kidney disease
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(if using contrast)
• claustrophobia?
• Short bore
Latest…
high field
 >1.5 Tesla
 advantages of tunnel and open MRIs
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MRI
• Pros
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More accurate 3-D image
Good structural detail
No radiation
• Cons
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$$$
Time consuming
Won’t show recent hemorrhage
Case #3.
• 46 YOWF
• CC: Time to change her glasses
• HabRx:
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OD –4.25 DS
OS –5.00 DS
• BVA
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OD: -4.00 20/20
OS: -0.25 20/20
Other Imaging Tests…
Magnetic Resonance
Angiography (MRA)
• Non-invasive method for investigation of
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blood vessels
Surgical planning
3-D view
Picks up rapid blood flow
highly accurate for stenosis >50%
Positron Emission Tomography
(PET)
• Biochemical and physiologic function –
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in vivo
Radioactive “Tracer” compound
Injected or inhaled
 C, N, O, F
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 18F
labeled fluorodeoxyglucose
 Image of brain activity
Functional MRI (fMRI)
• Physiology of visual system
• With or without contrast
• Many advantages over PET
• The new “lie detector?”
So… You want to order a
scan??
Before You Order Tests...
• Good case history
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any contraindications??
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Comprehensive exam
Narrow ddx
Is there anything YOU can do?
Avoid “fishing expedition” or “shot-gun”
approaches
• Select most appropriate test
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MRI not always needed
Communicating with the Lab
• Which test(s)?
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with contrast?
Code?
Which insurance?
What do you want to view?
DDX?
Be available
Getting the Job Done
• Communicate with the Patient
Explain why imaging is necessary
 Explain the test
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• Insurance Issues
Can you order the test??
 Is the patient insured??
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If You Order Tests...
• Written report of findings and copies of
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the films
Communicate
Treat
Comanage / Refer
CLIA
• Clinical Laboratory Improvement Act
• regulates all lab tests performed on humans in
US
• ensures quality laboratory testing
• Waived tests
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determined by FDA or CDC to be so simple that
there is little risk of error
• www.cms.hhs.gov/clia
Missouri Contact
• Missouri Dept of Health and Senior
Services – CLIA Section
PO Box 570
 Jefferson City, MO 65102
 573-751-6318
 Contact: William Nugent
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CLIA
• can file for “Waived Status”
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approximately 40 tests
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random blood glucose
ESR
urine pregnancy tests
• must meet criteria:
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enroll in CLIA program
pay fees biennially ($150 for waived)
follow manufacturers’ test instructions
Glad you looked!
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58 year old female
CC: SpRx broken
OHx: unremarkable
MHx: unremarkable, no meds
20/20 OD; 20/20 OS
Random Blood Glucose
• note when patient ate last
e.g. 220 mg/dL pp 3 hours
 pp = post-prandial
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• diabetic if:
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 200 mg/dL with symptoms
• can do in-office
• encourage patients to do this!
Fasting Plasma Glucose
• no food or drink for 8-12 hours
• diabetes if  126 mg/dL
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must repeat if asymptomatic
• IFG = 100 – 125 mg/dL
• also increased with:
steroids
 stress
 diuretics
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What’s in a Name??
• home monitoring
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whole blood glucose
• laboratory methods
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plasma glucose
• plasma glucose usually 10-15% higher
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than whole blood
SOME home monitors calibrate to
plasma
Oral Glucose Tolerance Test (OGTT)
• 75 g oral glucose
• check urine and blood at intervals
• non-diabetic BS will return to fasting
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levels in 3 hours
diabetic if  200 mg/dL at 2 hours
impaired GT if  140 and < 200 mg/dL at
2 hours
not needed if FBS > 200 mg/dL
Glycosylated Hemoglobin
• HbA1c
• checks long-term control
• glycosylated HgB stays with RBC for its entire
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life
not diagnostic test?
normal = 4.3-6.1%
• diabetic goal < 7.0%
• ask patients!
• A1cNow (Metrika, Inc.)
• A1C Now InView multitest system
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CPT 83036QW
Glycoslyated Hemoglobin
A1C
Blood Glucose
Levels
12%
345 mg/dL
11
310
10
275
9
240
8
205
7
170
6
135
5
100
4
65
1% A1C
= 30 mg/dL
What Can We Do?
• Pre-diabetes – new term!
• 61% of US adults overweight
• Diabetes Prevention Program
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pts with IGT (N=3234)
lifestyle changes vs metformin vs placebo
reduced risk
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58% with lifestyle
– 30 minutes daily activity; weight loss of 5-7% BW
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31% with medication
• Educate patients
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honesty best policy…
Make Sure Your Diabetics Know Their ABCs
• A1c
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< 7.0%
• Blood Pressure
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< 130/80
• Cholesterol
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LDL <100 mg/dL
HDL > 45
Triglycerides < 200
statin use if TC  135 mg/dL
• www.diabetes.org
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67% didn’t know!
Diabetes PHD (personal health decisions)
Fasting Plasma Glucose
• fluctuating vision
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get stable reading before new SpRx
retinopathy
diplopia
vascular occlusions
optic neuropathy
HIV Testing
• Home-use HIV test kits
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NOT FDA approved
Available on Internet
• FDA-approved Home sample collection kits
• Enzyme Immunoassay
• Western Blot
• Nucleic acid testing (viral load)
OraQuick Rapid HIV-1/2 Antibody
Test
• approved in 2002 for testing with blood
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HIV-1 and HIV-2
CLIA waived status
• March 26, 2004
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approved using oral fluid
results in 20 minutes!
only for HIV-1
not for screening blood donors
not CLIA waived status yet
• 31% do NOT return for HIV testing results
• Also Uni-Gold Recombigen HIV (7/2004)