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LABORATORY TESTING IN PRIMARY CARE OPTOMETRY Tammy P. Than, MS, OD, FAAO Carl Vinson VAMC Dublin, GA tammy.than@va.gov Microbiology Cultures and Sensitivities Mandatory central corneal ulcers hyperacute conjunctivitis ophthalmia neonatorum membranous conjunctivitis

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laboratory testing in primary care optometry

LABORATORY TESTING IN PRIMARY CARE OPTOMETRY

Tammy P. Than, MS, OD, FAAO

Carl Vinson VAMC

Dublin, GA

tammy.than@va.gov

cultures and sensitivities
Cultures and Sensitivities
  • Mandatory
    • central corneal ulcers
    • hyperacute conjunctivitis
    • ophthalmia neonatorum
    • membranous conjunctivitis
    • Parinaud’s oculoglandular syndrome
    • postoperative infections
  • Recommended
    • chronic conjunctivitis
    • unresponsive conjunctivitis
    • new practitioner
cultures and sensitivities4
Cultures and Sensitivities
  • specimen preparation is important
  • no anesthetic – if possible
  • sterile swab  plate onto culture media
  • culturette
  • media:
    • Thioglycolate broth
    • Blood agar
    • Chocolate agar
    • Saboraud’s agar
transport media
Transport Media
  • Amies media without charcoal
    • Higher yield than other media
    • Comparable to plates
in office microbiology
In-Office Microbiology
  • Gram Stain
    • Gram (+) = purple
    • Gram (-) = pink
    • look at morphology
  • Cytology
    • PMNs = bacterial
    • lymphocytes = viral
    • eosinophils = allergic
diagnostic imaging
Diagnostic Imaging
  • plain film X-Ray
  • CT scan
  • MRI
    • 75 million in 2003
  • Ultrasonography
  • Angiography
  • GDx, OCT, HRT
  • etc…
resources
Resources
  • Imaging of the Globe and Orbit: A Guide to Differential Diagnosis
    • Hosten and Bornfield
    • Publisher Thieme
  • http://www.med.harvard.edu/AANLIB/home.html
  • http://www.loni.ucla.edu/index.shtml
x ray the basics
X-Ray: The Basics
  • Incident X-Ray enters tissue
  • Beam is attenuated
  • Exit X-Ray leaves tissue exposes film
    • 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
X-Ray: Types of Views
  • Skull / Sinus Series
    • Caldwell
    • Lateral
    • Waters
  • Chest
    • AP, PA, lateral
  • Spinal
x ray indications
X-Ray Indications
  • Confirm the integrity of the orbit
    • Intraocular Foreign Body
    • Intraorbital Foreign Body
  • Trauma
    • muscle entrapment?
x ray indications18
X-Ray Indications
  • Sinusitis
    • R/O Orbital cellulitis
  • Horner’s syndrome
  • Uveitis
  • Ankylosing spondylitis
  • Reiter’s syndrome
x ray contraindications
X-Ray: Contraindications
  • Pregnancy
  • Excessive Radiation Exposure
    • Rad = unit of absorbed energy in tissue
    • Gray (Gy) = 100 Rad
      • 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
X-Rays
  • Pros
    • Inexpensive
    • Readily available
    • Rapid results
  • Cons
    • Radiation exposure
    • No information about soft tissue
    • 2-D interpretation can be difficult
case 1
Case #1
  • 17 YOM
  • Hit in eye x 1 day
  • + pain
  • +diplopia
work up
Work-Up
  • EOMs
  • Exophthalmometry
  • Crepitus?
  • Nerve sensation
  • IOP
  • Imaging
management
Management
  • Nasal decongestants
  • Oral antibiotics
    • broad spectrum
      • e.g. Keflex 500 mg qid
  • Don’t blow nose!
  • +/- Sx in 1-2 weeks
other considerations
Other Considerations…
  • R/O Seidel’s sign
  • Anterior Segment Pathology
    • uveitis
    • corneal abrasion
    • subconjunctival hemorrhage
  • Commotio Retinae
ct scan the basics
CT Scan: The Basics
  • Series of thin X-Ray sections
    • flat panel detectors may eliminate slices
  • Emitted X-Rays
  • Diode sensors
  • Computer reconstructs views
ct scan the basics26
CT Scan: The Basics
  • CT Numbers
    • density < water = negative CT#
    • density > water = positive CT#
  • “Windowing”
  • Gray Scale
    • White = bone
    • Black = air
    • Gray = brain
ct scan
CT Scan
  • Views
    • coronal
      • paranasal sinuses, orbital integrity
    • sagittal
      • chiasmal pathology
    • axial
      • orbital and visual pathways
ct the exam
CT – The Exam
  • Specific protocols
    • orbital
    • chiasmal
    • brain
    • sinuses
  • Slice thickness and slice increment
  • Cranial
    • ~1 cm / no overlap
  • Orbital and Chiasmal
    • 3 mm with 2 mm between
    • allows overlap
  • Gantry
  • 10-20 minutes / scan
contrast
Contrast
  • Iodine
    • 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
    • d/c Metformin (Glucophage) prior to procedure
  • CI is shellfish allergy
bun blood urea nitrogen
BUN (Blood Urea Nitrogen)
  • actually performed on serum or plasma
    • 12% higher than blood
  • nitrogen portion of urea
  • urea is formed in liver from protein breakdown
  • filtered through renal glomeruli
    • small amount reabsorbed in the tubules
    • remainder excreted in urine
  • azotemia – elevated BUN
    • nonspecific
    • prerenal, renal, or postrenal
bun blood urea nitrogen31
BUN (Blood Urea Nitrogen)
  • must be compared over time or evaluated with other tests
    • renal function – also assess creatinine levels
  • fasting not required
  • Adult 5-20 mg/dL
  • >60 8-21 mg/dL
  • increased BUN
    • many conditions and many drugs
  • decreased BUN
    • alcohol abuse, diet lacking protein, liver destruction, late pregnancy
creatinine
CREATININE
  • product of anaerobic energy-producing creatine-phosphate metabolism in skeletal muscle
  • excreted by kidneys
    • increased levels indicative of decreased glomerular filtration rate
  • Avoid excessive exercise for 8 hours and avoid excessive red meat for 24 hours before testing
creatinine33
CREATININE
  • Normal
    • females 0.5 – 1.1 mg/dL
    • males 0.6 –1.2 mg/dL
    • elderly – may be lower
  • Creatinine clearance, urine
    • 24 hour collection
  • Creatinine clearance, serum urine
    • 6, 12, or 24 hour collection
    • blood sample collected anytime during urine collection period
ct scan artifacts
CT Scan: Artifacts
  • Motion
  • Dental Fillings
  • Partial volume phenomenon
ct indications
CT Indications
  • bone imaging
  • calcification
  • blood detection
    • acute
  • meningiomas
  • when MRI contraindicated
ct contraindications
CT Contraindications
  • pregnancy
  • excessive radiation exposure
  • contrast contraindication
    • iodine sensitivity
    • shellfish allergy
    • kidney disease
ct scan37
CT Scan
  • Pros
    • High diagnostic yield
    • Good for bone
    • Can reconstruct different views
  • Cons
    • Expensive
    • Human risk
    • Motion artifacts
    • Hard to ddx tumors
slide38
MRI

Unpaired protons (H) = tiny magnets

    • from water and fat
    • body is 63% hydrogen atoms
  • Disrupt with radio pulse
  • Protons return to original state
  • Release energy -> MRI
slide39
MRI
  • Signal strength: proton density
  • Relaxation time: surrounding tissue
  • T1 weighted
    • Proton density
    • tissue composition
  • T2 weighted
    • Tissue differences
  • Intermediate
  • fat suppression
slide40
MRI
  • White Matter and Fat
    • T1 = bright T2 = dark
  • Gray Matter and CSF
    • T1 = dark T2 = bright
  • Vitreous
    • T1 = dark T2 = bright
  • blood, air = black
  • EOMs and optic nerves = intermediate density
mri the examination
MRI: The Examination
  • Gantry
  • Flux
    • 0.5 – 1.5 Tesla
  • Energy detected
  • Image reconstructed
  • 40 minutes
  • +/- gadolinium contrast
    • paramagnetic
    • highlights images of similar density
mri indications
MRI Indications
  • tumors
    • posterior visual pathway
    • brain stem
    • pituitary
  • infarcts
  • posterior fossa
  • MS
mri indications43
MRI Indications
  • elevated optic nerve head(s)
  • unilateral proptosis
  • field loss
    • hemianopia
    • bitemporal
  • cranial nerve palsies
mri contraindications
MRI Contraindications
  • pregnancy
  • metallic FB
  • pacemakers
  • kidney disease
    • (if using contrast)
  • claustrophobia?
latest
Latest…
  • Short bore
    • high field
    • >1.5 Tesla
    • advantages of tunnel and open MRIs
slide46
MRI
  • Pros
    • More accurate 3-D image
    • Good structural detail
    • No radiation
  • Cons
    • $$$
    • Time consuming
    • Won’t show recent hemorrhage
case 3
Case #3.
  • 46 YOWF
  • CC: Time to change her glasses
  • HabRx:
    • OD –4.25 DS
    • OS –5.00 DS
  • BVA
    • OD: -4.00 20/20
    • OS: -0.25 20/20
magnetic resonance angiography mra
Magnetic Resonance Angiography (MRA)
  • Non-invasive method for investigation of blood vessels
  • Surgical planning
  • 3-D view
  • Picks up rapid blood flow
  • highly accurate for stenosis >50%
positron emission tomography pet
Positron Emission Tomography (PET)
  • Biochemical and physiologic function – in vivo
  • Radioactive “Tracer” compound
    • Injected or inhaled
    • C, N, O, F
      • 18F labeled fluorodeoxyglucose
      • Image of brain activity
functional mri fmri
Functional MRI (fMRI)
  • Physiology of visual system
  • With or without contrast
  • Many advantages over PET
  • The new “lie detector?”
before you order tests
Before You Order Tests...
  • Good case history
    • any contraindications??
  • Comprehensive exam
  • Narrow ddx
  • Is there anything YOU can do?
  • Avoid “fishing expedition” or “shot-gun” approaches
  • Select most appropriate test
    • MRI not always needed
communicating with the lab
Communicating with the Lab
  • Which test(s)?
    • with contrast?
  • Code?
  • Which insurance?
  • What do you want to view?
  • DDX?
  • Be available
getting the job done
Getting the Job Done
  • Communicate with the Patient
    • Explain why imaging is necessary
    • Explain the test
  • Insurance Issues
    • Can you order the test??
    • Is the patient insured??
if you order tests
If You Order Tests...
  • Written report of findings and copies of the films
  • Communicate
  • Treat
  • Comanage / Refer
slide57
CLIA
  • Clinical Laboratory Improvement Act
  • regulates all lab tests performed on humans in US
  • ensures quality laboratory testing
  • Waived tests
    • determined by FDA or CDC to be so simple that there is little risk of error
  • www.cms.hhs.gov/clia
missouri contact
Missouri Contact
  • Missouri Dept of Health and Senior Services – CLIA Section
    • PO Box 570
    • Jefferson City, MO 65102
    • 573-751-6318
    • Contact: William Nugent
slide59
CLIA
  • can file for “Waived Status”
    • approximately 40 tests
      • random blood glucose
      • ESR
      • urine pregnancy tests
  • must meet criteria:
    • enroll in CLIA program
    • pay fees biennially ($150 for waived)
    • follow manufacturers’ test instructions
glad you looked
Glad you looked!
  • 58 year old female
  • CC: SpRx broken
  • OHx: unremarkable
  • MHx: unremarkable, no meds
  • 20/20 OD; 20/20 OS
random blood glucose
Random Blood Glucose
  • note when patient ate last
    • e.g. 220 mg/dL pp 3 hours
    • pp = post-prandial
  • diabetic if:
    •  200 mg/dL with symptoms
  • can do in-office
  • encourage patients to do this!
fasting plasma glucose
Fasting Plasma Glucose
  • no food or drink for 8-12 hours
  • diabetes if  126 mg/dL
    • must repeat if asymptomatic
  • IFG = 100 – 125 mg/dL
  • also increased with:
    • steroids
    • stress
    • diuretics
what s in a name
What’s in a Name??
  • home monitoring
    • whole blood glucose
  • laboratory methods
    • plasma glucose
  • plasma glucose usually 10-15% higher than whole blood
  • SOME home monitors calibrate to plasma
oral glucose tolerance test ogtt
Oral Glucose Tolerance Test (OGTT)
  • 75 g oral glucose
  • check urine and blood at intervals
  • non-diabetic BS will return to fasting 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
Glycosylated Hemoglobin
  • HbA1c
  • checks long-term control
  • glycosylated HgB stays with RBC for its entire life
  • not diagnostic test?
  • normal = 4.3-6.1%
  • diabetic goal < 7.0%
  • ask patients!
  • A1cNow (Metrika, Inc.)
  • A1C Now InView multitest system
    • CPT 83036QW
glycoslyated hemoglobin
Glycoslyated Hemoglobin
  • 1% A1C = 30 mg/dL
what can we do
What Can We Do?
  • Pre-diabetes – new term!
  • 61% of US adults overweight
  • Diabetes Prevention Program
    • pts with IGT (N=3234)
    • lifestyle changes vs metformin vs placebo
    • reduced risk
      • 58% with lifestyle
        • 30 minutes daily activity; weight loss of 5-7% BW
      • 31% with medication
  • Educate patients
    • honesty best policy…
make sure your diabetics know their abcs
Make Sure Your Diabetics Know Their ABCs
  • A1c
    • < 7.0%
  • Blood Pressure
    • < 130/80
  • Cholesterol
    • LDL <100 mg/dL
    • HDL > 45
    • Triglycerides < 200
    • statin use if TC  135 mg/dL
  • www.diabetes.org
    • 67% didn’t know!
    • Diabetes PHD (personal health decisions)
fasting plasma glucose69
Fasting Plasma Glucose
  • fluctuating vision
    • get stable reading before new SpRx
  • retinopathy
  • diplopia
  • vascular occlusions
  • optic neuropathy
hiv testing
HIV Testing
  • Home-use HIV test kits
    • 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
OraQuick Rapid HIV-1/2 Antibody Test
  • approved in 2002 for testing with blood
    • HIV-1 and HIV-2
    • CLIA waived status
  • March 26, 2004
    • 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)