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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... • • • • 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 • • • • get stable reading before new SpRx retinopathy diplopia vascular occlusions optic neuropathy CASE EXAMPLES Case #1. This is an easy one! • • • • 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 • • • • 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) • • • • each lab has normal value normal range is 2 secs Adult 10-15 sec International Normalized Ratio (INR) 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 • • functioning time for recalcified, citrate plasma takes to clot after partial thromboplastin is added Activated PTT commercial activating materials used to standardize the test current method of the test • Standardized times reported by each lab < 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 • • • • RBC count hemoglobin morphology hematocrit volume of RBC in 100 mL 3 x Hgb • platelets Coagulation Studies • • • • recurrent subconjunctival hemorrhages non-traumatic hyphema artery or vein occlusion pre-op cataract surgery? Case #2. To Treat or not to Treat. • • • • 34 YOWF CC: HAs, double vision, dizzy OHx: no trauma, LEE in 1999 - normal MHx: Voltaren, Zantac Exam Findings • • • • 20/20 OD; 20/20 OS PERRL / (-)APD partial 6th nerve palsy (OS) visual field defects superior nasal step OD increased blind spot OS Fundus: What’s Your Diagnosis? • • • • papilledema R/O mass R/O infection placing your bets... Idiopathic Intracranial Hypertension Workup • CT or MRI unremarkable • LP normal CSF content elevated pressure Management • weight loss • acetazolamide Diamox • steroids?? • ON sheath decompression • LP shunt Before you prescribe Diamox • baseline electrolytes • CBC with differential R/O blood dyscrasias • monitor every 6 months Electrolytes • Na+ 135.0 – 145.0 mmol/L • K+ 3.60 – 5.00 mmol/L • Cl 101.0 – 111.0 mmol/L CO2 total content blood • 21.0 – 31.0 mmol/L • Increased alcoholism airway obstruction pneumonia drugs (e.g. antacids) • Decreased dehydration Diamox 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 Carbon dioxide Chloride Creatinine Potassium Sodium Urea nitrogen SMA-7 Carbon dioxide Chloride Creatinine Glucose Potassium Sodium Urea nitrogen SMA-12 Albumin Alkaline phosphatase Aspartate aminotransferase Bilirubin Calcium Cholesterol Glucose Lactate dehydrogenase Phosphorus Protein Urea nitrogen Uric acid • Also SMA-20 Eyelid Xanthoma • • • • 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 • • • • 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 > • • • • 200 mg/dL desirable: 160-200 mg/dL borderline: 200-239 mg/dL high 240 mg/dL Outside US cholesterol x 0.0259 mmoles/L (international units) 200 mg/dL = 5.18 mmol/L More Numbers… • HDL good 35 mg/dL women probably 45 mg/dL 1 mg/mL risk of CHD 2-3% Helsinki Heart Study (gemfibrizol in men ) • LDL good < 130 mg/dL high 190 mg/dL • Ratio (Total / HDL) < 5:1 Female < 4.4 Triglycerides • normal < 200 mg/dL women probably < 150 • borderline 200-400 • high 400-1000 • very high > 1000 Lipid Panel • arcus young patients • occlusive disease • optic neuropathy • xanthoma CASE #3 Case #3 • • • • • 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 two dot hemorrhages OD Initial Presentation • OD – unremarkable What is your tentative diagnosis? • • • • • • • 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 • • • • • • 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 • • • • liver during acute inflammation disappears rapidly once inflammation subsides 4 hour fast from food/fluids alternative to ESR more informative ESR high in most elderly no cross interference • normal: no CRP Causes of Optic Nerve Edema • • • • • • • • • • • 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 • unilateral or bilateral asymmetric Diabetic Papillopathy • retinopathy does not need to be present • small optic nerve cupping 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 • pathophysiology is unclear Diabetic Papillopathy • Eye 2005 19:45-51 6 eyes Betamethasone – Subtenons’ injection duration decreased from 5 months to 3 weeks • Am J Ophth 2004 137(6) 1151-3 1 case – intravitreal triamcinolone significant improvement in visual acuity CASE #4 “Phone A Friend” • • • • • • 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 OD 20/60 PH 20/30 OS 20/50 PH 20/30 • Refraction OD -2.00 –1.75 x 135 20/25 -2.00 –5.00 x 167 20/50 • K readings… OD 39.75 / 44.12 @ 095 OS 36.75 / 43.50 @ 095 • Cornea central corneal edema with “haziness” What’s Your Tentative Diagnosis? • 1. Keratoconus • 2. Keratoconus with Acute Corneal • • • • • 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: acute: dense, white stromal necrosis vascularization (salmon patch of Hutchinson) later: scarring and thinning ghost vessels Interstitial Keratitis • • • • • • • • 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 rapid plasma reagin test • VDRL venereal disease research laboratory test • Treat If: (+) RPR and (+)FTA-ABS • What if: (+)RPR and (-)FTA-ABS PPD • purified protein • • • • • 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 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 • Inactive 50% of bilateral Syphilis • All cases 20% attributed to syphilis