LABORATORY TESTING IN PRIMARY CARE OPTOMETRY

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LABORATORY TESTING IN PRIMARY CARE OPTOMETRY

• Tammy P. Than, MS, OD, FAAO
• Carl Vinson VAMC
• Dublin, GA
• tammy.than_at_va.gov

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Microbiology
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Cultures and Sensitivities

• Mandatory
• central corneal ulcers
• hyperacute conjunctivitis
• ophthalmia neonatorum
• membranous conjunctivitis
• Parinauds oculoglandular syndrome
• postoperative infections
• Recommended
• chronic conjunctivitis
• unresponsive conjunctivitis
• new practitioner

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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
• Saborauds agar

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Transport Media

• Amies media without charcoal
• Higher yield than other media
• Comparable to plates

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In-Office Microbiology

• Gram Stain
• Gram () purple
• Gram (-) pink
• look at morphology
• Cytology
• PMNs bacterial
• lymphocytes viral
• eosinophils allergic

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Diagnostic Imaging

• plain film X-Ray
• CT scan
• MRI
• 75 million in 2003
• Ultrasonography
• Angiography
• GDx, OCT, HRT
• etc

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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

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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

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X-Ray Types of Views

• Skull / Sinus Series
• Caldwell
• Lateral
• Waters
• Chest
• AP, PA, lateral
• Spinal

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CALDWELL
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CALDWELL
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LATERAL
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LATERAL
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WATERS
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WATERS
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X-Ray Indications

• Confirm the integrity of the orbit
• Intraocular Foreign Body
• Intraorbital Foreign Body
• Trauma
• muscle entrapment?

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X-Ray Indications

• Sinusitis
• R/O Orbital cellulitis
• Horners syndrome
• Uveitis
• Ankylosing spondylitis
• Reiters syndrome

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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 lt 1 cGy
• cancer treatment may be 6000 cGy
• lens is most sensitive

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X-Rays

• Pros
• Inexpensive
• Readily available
• Rapid results
• Cons
• Radiation exposure
• No information about soft tissue
• 2-D interpretation can be difficult

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Case 1

• 17 YOM
• Hit in eye x 1 day
• pain
• diplopia

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Work-Up

• EOMs
• Exophthalmometry
• Crepitus?
• Nerve sensation
• IOP
• Imaging

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Management

• Nasal decongestants
• Oral antibiotics
• broad spectrum
• e.g. Keflex 500 mg qid
• Dont blow nose!
• /- Sx in 1-2 weeks

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Other Considerations

• R/O Seidels sign
• Anterior Segment Pathology
• uveitis
• corneal abrasion
• subconjunctival hemorrhage
• Commotio Retinae

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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
• density lt water negative CT
• density gt water positive CT
• Windowing
• Gray Scale
• White bone
• Black air
• Gray brain

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CT Scan

• Views
• coronal
• paranasal sinuses, orbital integrity
• sagittal
• chiasmal pathology
• axial
• orbital and visual pathways

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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

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Contrast

• Iodine
• good agent for photoelectric capture
• enhances visibility of vascular lesions
• Administered IV (or intrathecal)
• 140,000 incident of AE
• BUN and Creatinine
• NPO
• Good medication hx
• d/c Metformin (Glucophage) prior to procedure
• CI is shellfish allergy

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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

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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
• gt60 8-21 mg/dL
• increased BUN
• many conditions and many drugs
• decreased BUN
• alcohol abuse, diet lacking protein, liver
  destruction, late pregnancy

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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

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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

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CT Scan Artifacts

• Motion
• Dental Fillings
• Partial volume phenomenon

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CT Indications

• bone imaging
• calcification
• blood detection
• acute
• meningiomas
• when MRI contraindicated

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CT Contraindications

• pregnancy
• excessive radiation exposure
• contrast contraindication
• iodine sensitivity
• shellfish allergy
• kidney disease

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CT Scan

• Pros
• High diagnostic yield
• Good for bone
• Can reconstruct different views
• Cons
• Expensive
• Human risk
• Motion artifacts
• Hard to ddx tumors

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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 -gt MRI

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MRI

• Signal strength proton density
• Relaxation time surrounding tissue
• T1 weighted
• Proton density
• tissue composition
• T2 weighted
• Tissue differences
• Intermediate
• fat suppression

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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

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MRI The Examination

• Gantry
• Flux
• 0.5 1.5 Tesla
• Energy detected
• Image reconstructed
• 40 minutes
• /- gadolinium contrast
• paramagnetic
• highlights images of similar density

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MRI Indications

• tumors
• posterior visual pathway
• brain stem
• pituitary
• infarcts
• posterior fossa
• MS

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MRI Indications

• elevated optic nerve head(s)
• unilateral proptosis
• field loss
• hemianopia
• bitemporal
• cranial nerve palsies

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MRI Contraindications

• pregnancy
• metallic FB
• pacemakers
• kidney disease
• (if using contrast)
• claustrophobia?

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Latest

• Short bore
• high field
• gt1.5 Tesla
• advantages of tunnel and open MRIs

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MRI

• Pros
• More accurate 3-D image
• Good structural detail
• No radiation
• Cons
• Time consuming
• Wont show recent hemorrhage

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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

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Other Imaging Tests
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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 gt50

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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

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Functional MRI (fMRI)

• Physiology of visual system
• With or without contrast
• Many advantages over PET
• The new lie detector?

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So You want to order a scan??
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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

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Communicating with the Lab

• Which test(s)?
• with contrast?
• Code?
• Which insurance?
• What do you want to view?
• DDX?
• Be available

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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??

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If You Order Tests...

• Written report of findings and copies of the
  films
• Communicate
• Treat
• Comanage / Refer

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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

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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
• 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

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Glad you looked!

• 58 year old female
• CC SpRx broken
• OHx unremarkable
• MHx unremarkable, no meds
• 20/20 OD 20/20 OS

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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!

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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

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Whats 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

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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 lt 200 mg/dL at 2 hours
• not needed if FBS gt 200 mg/dL

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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 lt 7.0
• ask patients!
• A1cNow (Metrika, Inc.)
• A1C Now InView multitest system
• CPT 83036QW

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Glycoslyated Hemoglobin

• 1 A1C 30 mg/dL

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What Can We Do?

• Pre-diabetes new term!
• 61 of US adults overweight
• Diabetes Prevention Program
• pts with IGT (N3234)
• 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

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Make Sure Your Diabetics Know Their ABCs

• A1c
• lt 7.0
• Blood Pressure
• lt 130/80
• Cholesterol
• LDL lt100 mg/dL
• HDL gt 45
• Triglycerides lt 200
• statin use if TC ? 135 mg/dL
• www.diabetes.org
• 67 didnt know!
• Diabetes PHD (personal health decisions)

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Fasting Plasma Glucose

• fluctuating vision
• get stable reading before new SpRx
• retinopathy
• diplopia
• vascular occlusions
• optic neuropathy

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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)

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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)