Transcript Laboratory Testing: Its Role in Diagnosing and Managing

How and When to Order
Blood Tests
Tammy Pifer Than, MS, OD, FAAO
Carl Vinson VAMC
Dublin, GA
[email protected]
Getting the Job Done...
• PCP
• External laboratory
• In-office sampling

is it ok?
Before You Order Tests...
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good case hx
narrow ddx
avoid “shot gun” approach
comprehensive ocular exam
If You Order Tests...
• interpret

Laboratory Tests and Diagnostic Procedures


4th edition - 2004
Chernecky and Berger
– includes Herbal interactions


ISBN 0721603882
$41.95
• communicate
• treat
• refer
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!
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!
Fasting Plasma Glucose
• fluctuating vision
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get stable reading before new SpRx
retinopathy
diplopia
vascular occlusions
optic neuropathy
CASE EXAMPLES
Case #1. This is an easy one!
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17 year old male
CC: eyes look “real bad”
Symptoms: no pain
Pertinent Hx: county fair last night
Subconjunctival Hemorrhage
• History
frequency
 medications
 activity

• Examination
Subconjunctival Hemorrhage
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Blood pressure
CBC with differential
PT (prothrombin time)
PTT (partial thromboplastin time)

or APTT (activated PTT)
• INR (international normalized ratio)
Prothrombin Time (PT)
• prothrombin:


vitamin-K dependent glycoprotein produced by
liver
needed for firm fibrin clot formation
• PT – measures time for clot formation

reagent tissue thromboplastin and calcium are
added to citrate plasma
• avoid coffee and alcohol for 24 hours before
test
Prothrombin Time (PT)
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each lab has normal value
normal range is  2 secs
Adult 10-15 sec
International Normalized Ratio (INR)
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standardizes PT results
INR = (Patient’s PT in seconds)ISI
Mean normal PT in seconds
ISI = international sensitivity index
Coumadin therapy
Partial Thromboplastin Time (PTT)
• evaluates how well coagulation sequence is
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functioning
time for recalcified, citrate plasma takes to clot
after partial thromboplastin is added
Activated PTT
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commercial activating materials used to standardize
the test
current method of the test
• Standardized times reported by each lab
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< 35 seconds
CBC with differential
• routine part of health care
• inexpensive
• screening:
anemia
 leukemia
 infection
 inflammation

WBC (Part of CBC)
• Total
overall number
 first line of defense
 decreased in aplastic anemia
 elevated in infections, leukemia

WBC (Part of CBC)
• Differential
100 white blood cells
 % of each
 neutrophils
 lymphocytes
 monocytes
 eosinophils & basophils

CBC
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RBC count
hemoglobin
morphology
hematocrit
volume of RBC in 100 mL
 3 x Hgb
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• platelets
Coagulation Studies
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recurrent subconjunctival hemorrhages
non-traumatic hyphema
artery or vein occlusion
pre-op cataract surgery?
Case #2. To Treat or not to Treat.
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34 YOWF
CC: HAs, double vision, dizzy
OHx: no trauma, LEE in 1999 - normal
MHx: Voltaren, Zantac
Exam Findings
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20/20 OD; 20/20 OS
PERRL / (-)APD
partial 6th nerve palsy (OS)
visual field defects
superior nasal step OD
 increased blind spot OS
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Fundus: What’s Your Diagnosis?
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papilledema
R/O mass
R/O infection
placing your bets...
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Idiopathic Intracranial Hypertension
Workup
• CT or MRI
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unremarkable
• LP
normal CSF content
 elevated pressure
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Management
• weight loss
• acetazolamide
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Diamox
• steroids??
• ON sheath decompression
• LP shunt
Before you prescribe Diamox
• baseline electrolytes
• CBC with differential
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R/O blood dyscrasias
• monitor every 6 months
Electrolytes
• Na+
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135.0 – 145.0 mmol/L
• K+
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3.60 – 5.00 mmol/L
• Cl
101.0 – 111.0 mmol/L
CO2 total content blood
• 21.0 – 31.0 mmol/L
• Increased
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alcoholism
airway obstruction
pneumonia
drugs (e.g. antacids)
• Decreased
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dehydration
Diamox
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measures compliance - < 20 mEq/L
tetracyclines
SMA-6
• Sequential multiple analyzer (SMA)
• automated system that analyzes multiple blood
values from one tube of blood
• SMA-6
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Carbon dioxide
Chloride
Creatinine
Potassium
Sodium
Urea nitrogen
SMA-7
Carbon dioxide
 Chloride
 Creatinine
 Glucose
 Potassium
 Sodium
 Urea nitrogen
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SMA-12
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Albumin
Alkaline phosphatase
Aspartate aminotransferase
Bilirubin
Calcium
Cholesterol
Glucose
Lactate dehydrogenase
Phosphorus
Protein
Urea nitrogen
Uric acid
• Also SMA-20
Eyelid Xanthoma
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dermis infiltrated with xanthoma cells
yellow bilateral plaque
medial aspect UL
management:
 cautery
 laser
 anything
else?
Lipid Panel/Profile
• 12 hour fasting
• total cholesterol
• LDL
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Usually calculated
LDL = cholesterol X (HDL+Triglycerides)/2
HDL
triglycerides
risk for CAD
ratio total cholesterol / HDL
Cholesterol
• over half of adults in US have cholesterol >
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200 mg/dL
desirable: 160-200 mg/dL
borderline: 200-239 mg/dL
high  240 mg/dL
Outside US
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cholesterol x 0.0259 mmoles/L (international units)
200 mg/dL = 5.18 mmol/L
More Numbers…
• HDL
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good  35 mg/dL
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women probably  45 mg/dL
 1 mg/mL risk of CHD  2-3%
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Helsinki Heart Study (gemfibrizol in men )
• LDL
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good < 130 mg/dL
high  190 mg/dL
• Ratio (Total / HDL)
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< 5:1
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Female < 4.4
Triglycerides
• normal < 200 mg/dL
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women probably < 150
• borderline 200-400
• high 400-1000
• very high > 1000
Lipid Panel
• arcus
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young patients
• occlusive disease
• optic neuropathy
• xanthoma
CASE #3
Case #3
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52 YOWM
CC: “inferior vision OS is dim”
MHx: diabetic x 20 years; poor control
VAs: OD 20/20 OS 20/20-2
LEE: 6 month prior
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two dot hemorrhages OD
Initial Presentation
• OD – unremarkable
What is your tentative
diagnosis?
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1.
2.
3.
4.
5.
6.
7.
Anterior ischemic optic neuropathy
Retrobulbar mass
Papilledema
Diabetic papillopathy
Optic Neuritis
Papillitis
Other?
What Should You Do?
ESR
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erythrocyte sedimentation rate
nonspecific test for inflammation
mm/hr
M: age/2
F: (age+10)/2
usually > 60 mm/hr in GCA
C-Reactive Protein (CRP)
• abnormal serum glycoprotein produced by
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liver during acute inflammation
disappears rapidly once inflammation subsides
4 hour fast from food/fluids
alternative to ESR
more informative
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ESR high in most elderly
no cross interference
• normal: no CRP
Causes of Optic Nerve
Edema
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Arteritic Ischemic Optic Neuropathy
Nonarteritic Ischemic Optic Neuropathy
Central Retinal Vein Occlusion
Compressive Optic Nerve Head Tumor
Diabetic Papillopathy
Infiltration of Optic Nerve Head
Malignant Hypertension
Papilledema
Papillitis
Papillophlebitis
Thyroid Ophthalmopathy
Diabetic Papillopathy
• 0.4 – 2% of diabetics
• characteristics
sectoral or total ON edema
 ± peripapillary hemorrhages
 ± nerve fiber layer infarcts
 ± macular edema
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• unilateral or bilateral
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asymmetric
Diabetic Papillopathy
• retinopathy does not need to be present
• small optic nerve cupping
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 0.3/0.3
• usually associated with Type 1 DM?
• prognosis:
signficant or complete recovery in several
months
 may have residual pallor and VF defect
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• pathophysiology is unclear
Diabetic Papillopathy
• Eye 2005 19:45-51
6 eyes
 Betamethasone – Subtenons’ injection
 duration decreased from 5 months to 3
weeks
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• Am J Ophth 2004 137(6) 1151-3
1 case – intravitreal triamcinolone
 significant improvement in visual acuity
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CASE #4
“Phone A Friend”
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40 YOBF
CC: “Decrease vision for 3 weeks”
HPI: OS worse than OD; no pain; acute
MHx: unremarkable
Meds: None
NKMA
“Phone A Friend”
• Entering Acuities
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OD 20/60 PH 20/30
OS 20/50 PH 20/30
• Refraction
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OD
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-2.00 –1.75 x 135 20/25
-2.00 –5.00 x 167 20/50
• K readings…
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OD 39.75 / 44.12 @ 095
OS 36.75 / 43.50 @ 095
• Cornea
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central corneal edema with “haziness”
What’s Your Tentative Diagnosis?
• 1. Keratoconus
• 2. Keratoconus with Acute Corneal
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Hydrops
3. Corneal Ulcer
4. Corneal Dystrophy / Corneal
Degeneration
5. Dry Eye Syndrome
6. Herpes Simplex Keratitis
7. Other
What Was Actually Done…
• Cycloplegic
• Muro 128 qid
• RTC 1 day
Interstitial Keratitis
• cellular infiltration of the corneal stroma
• no primary involvement of epi or endo
• characterized by:
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acute:

dense, white stromal necrosis
 vascularization (salmon patch of
Hutchinson)
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later:
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scarring and thinning
 ghost vessels
Interstitial Keratitis
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Syphilis (Congenital or Acquired)
TB
Lyme
Parasitic infection
HSV
Sarcoidosis
Leprosy
Misc.
Syphilis: Ever Had It?
• FTA-ABS
fluorescent treponemal antibody absorption
test
 ordered more frequently
 positive even after treatment

• MHA-TP

microhemagglutination treponemal pallidum
test
Syphilis: Do you have it now?
• RPR
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rapid plasma reagin test
• VDRL
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venereal disease research laboratory test
• Treat If:
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(+) RPR and (+)FTA-ABS
• What if:
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(+)RPR and (-)FTA-ABS
PPD
• purified protein
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derivative
TB skin test
inject under skin
check in 48-72 hours
positive is >10 mm
wheal
Positive for active
and inactive TB
Lyme titer
• In endemic areas...
• Normal: negative
ACE
• angiotensin converting enzyme
• Enzyme found primarily in lung epithelial cells
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Some in blood vessels and renal tissue
Converts angiotensin I to angiotensin II, a
vasopressor that also stimulates adrenal cortex to
produce aldosterone
• best for patients > 20 YO
• helps confirm dx of sarcoidosis

ACE elevated in 60%
Interstitial Keratitis
• Active
70% of unilateral  Herpes Simplex Virus
 60% of bilateral  Idiopathic
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• Inactive
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50% of bilateral  Syphilis
• All cases
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20% attributed to syphilis