1 / 60

How and When to Order Blood Tests

How and When to Order Blood Tests Tammy Pifer Than, MS, OD, FAAO Carl Vinson VAMC Dublin, GA tammy.than@va.gov 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

benjamin
Download Presentation

How and When to Order Blood Tests

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. How and When to Order Blood Tests Tammy Pifer Than, MS, OD, FAAO Carl Vinson VAMC Dublin, GA tammy.than@va.gov

  2. Getting the Job Done... • PCP • External laboratory • In-office sampling • is it ok?

  3. Before You Order Tests... • good case hx • narrow ddx • avoid “shot gun” approach • comprehensive ocular exam

  4. 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

  5. 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!

  6. 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!

  7. Fasting Plasma Glucose • fluctuating vision • get stable reading before new SpRx • retinopathy • diplopia • vascular occlusions • optic neuropathy

  8. CASE EXAMPLES

  9. 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

  10. Subconjunctival Hemorrhage • History • frequency • medications • activity • Examination

  11. Subconjunctival Hemorrhage • Blood pressure • CBC with differential • PT (prothrombin time) • PTT (partial thromboplastin time) • or APTT (activated PTT) • INR (international normalized ratio)

  12. 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

  13. 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

  14. 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

  15. CBC with differential • routine part of health care • inexpensive • screening: • anemia • leukemia • infection • inflammation

  16. WBC (Part of CBC) • Total • overall number • first line of defense • decreased in aplastic anemia • elevated in infections, leukemia

  17. WBC (Part of CBC) • Differential • 100 white blood cells • % of each • neutrophils • lymphocytes • monocytes • eosinophils & basophils

  18. CBC • RBC count • hemoglobin • morphology • hematocrit • volume of RBC in 100 mL • 3 x Hgb • platelets

  19. Coagulation Studies • recurrent subconjunctival hemorrhages • non-traumatic hyphema • artery or vein occlusion • pre-op cataract surgery?

  20. 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

  21. 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

  22. Fundus: What’s Your Diagnosis? • papilledema • R/O mass • R/O infection • placing your bets... • Idiopathic Intracranial Hypertension

  23. Workup • CT or MRI • unremarkable • LP • normal CSF content • elevated pressure

  24. Management • weight loss • acetazolamide • Diamox • steroids?? • ON sheath decompression • LP shunt

  25. Before you prescribe Diamox • baseline electrolytes • CBC with differential • R/O blood dyscrasias • monitor every 6 months

  26. Electrolytes • Na+ • 135.0 – 145.0 mmol/L • K+ • 3.60 – 5.00 mmol/L • Cl- • 101.0 – 111.0 mmol/L

  27. 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

  28. 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

  29. SMA-7 • Carbon dioxide • Chloride • Creatinine • Glucose • Potassium • Sodium • Urea nitrogen

  30. SMA-12 • Albumin • Alkaline phosphatase • Aspartate aminotransferase • Bilirubin • Calcium • Cholesterol • Glucose • Lactate dehydrogenase • Phosphorus • Protein • Urea nitrogen • Uric acid • Also SMA-20

  31. Eyelid Xanthoma • dermis infiltrated with xanthoma cells • yellow bilateral plaque • medial aspect UL • management: • cautery • laser • anything else?

  32. 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

  33. 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

  34. 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

  35. Triglycerides • normal < 200 mg/dL • women probably < 150 • borderline 200-400 • high 400-1000 • very high > 1000

  36. Lipid Panel • arcus • young patients • occlusive disease • optic neuropathy • xanthoma

  37. CASE #3

  38. 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

  39. Initial Presentation • OD – unremarkable

  40. What is your tentative diagnosis? • 1. Anterior ischemic optic neuropathy • 2. Retrobulbar mass • 3. Papilledema • 4. Diabetic papillopathy • 5. Optic Neuritis • 6. Papillitis • 7. Other?

  41. What Should You Do?

  42. ESR • erythrocyte sedimentation rate • nonspecific test for inflammation • mm/hr • M: age/2 • F: (age+10)/2 • usually > 60 mm/hr in GCA

  43. 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

  44. 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

  45. 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

  46. 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

  47. 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

  48. CASE #4

  49. “Phone A Friend” • 40 YOBF • CC: “Decrease vision for 3 weeks” • HPI: OS worse than OD; no pain; acute • MHx: unremarkable • Meds: None • NKMA

  50. “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”

More Related