Laboratory Testing for the Primary Care Optometrist

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1 General lab principles Indications for testing - Confirm a clinical diagnosis - Rule out a diagnosis - Manage a disease - Screen for a disease Sensitivity is the ability to show a positive result in a patient who actually does have the disease. Specificity is the ability to show a negative result in a patient who does not have the disease. False positive errors occur when a patient tests positive for a disease process, even when he/she does not have the disease process; this occurs when the test is non-specific. False negative errors occur when a patient will test negative for a disease process, but actually does have the disease; this occur when a test has a very high sensitivity. Indication Tests to Order Notes Emergency Eye Care Swollen optic nerve (r/o Giant Cell Arteritis) CRP Platelets Fibrinogen norms - Men: age/2 - Women (age+10)/2 CRP greater than 2.45 Microhyphema/ hyphema Arcus Schnyder Corneal Dystrophy Band Keratopathy CBC w/differential* Sickledex Prothrombin time PTT Protein C function Protein S function - Triglycerides Triglycerides Calcium Albumin Magnesium Kidney Function - Urea Nitrogen(BUN) - Creatinine Uric Acid (gout) PO4 (phosphoric acid) Conjunctival Corneal Disease Platelets greater than 400k/cmm Sickledex will be positive in sickle cell anemia and sickle cell trait. Will need electrophoresis for confirmation.

2 Subconjunctival Hemorrhage Episcleritis Scleritis Interstitial keratitis Phylectenuolosis Xanthelasma Ptosis Molluscum Contagiousum Kaposi Sarcoma CBC w/differential* INR PT Liver function tests Protein C Protein S (rheumatoid factor) Serum uric acid ANCA Uric Acid CH 50 (total complement assay) C3 C4 ANCA with anergy panel VDRL or RPR FTA-ABS or MHA-TP Chest X-ray Eyelid Disease Triglycerides Acetylcholine receptor antibody -blocking, binding, modulating Thyroid hormone -T3, T4, TSH AIDS AIDS

3 Anterior RPR/VDRL HLA-B27 / in children Uveitis Testing for Syphilis TB Sarcoid Lyme disease Rheumatologic diseases Posterior CRAO/BRAO Diabetic Retinopathy Cystoid Macular Degeneration Toxoplasmosis titer Serum lysozyme HLA-B51 HLA-A29 Toxocara titer If immunocompromised CMV, herpes simplex, varicella zoster, rubella Retinal Disease /CRP if greater than 55 Lipid profile Serum protein electrophoresis Protein C (if below 50) Protein S (if below 50) HbA1C HbA1C Testing for Toxoplasmosis Sarcoid Syphilis Rheumatologic diseases Toxocara Lyme disease TB /Herpes/AIDS/Rubella

4 Cotton Wool Spots CRVO/BRVO /CRP if greater than 55 Hemoglobin A1C PT/PTT, CRP, platelets if greater than 55 Lipid profile In younger patients Hemoglobin electrophoresis Cryglobulins Antiphospholipid antibodies Factor V Leiden mutation Protein C and S Antithrombin III mutation Prothrombin G20210A mutation Homocysteine levels Serum protein electrophoresis Chest x-ray Lipemia Retinalis Macroaneurysm Peripheral Retinal Neovascularization Triglycerides Hemoglobin A1C Sickledex Sickledex will be positive in sickle cell anemia and sickle cell trait. Will need hemoglobin electrophoresis for confirmation. Angioid Streaks Exophthalmos Superior Limbic Keratoconjunctivitis Serum alkaline phosphatase level Urine calcium (Paget disease) Sickle cell prep Hemoglobin electrophoresis Thyroid - TSH - T3 - T4 Thyroid - TSH - T3 - T4 Orbital Disease

5 Preseptal Cellulitis Orbital Cellulitis Dacryoadenitis Non-Glaucomatous Optic Neuropathy 6 th nerve palsy 7 th nerve palsy Kidney Function Blood cultures Blood cultures Acute - Chronic - - -canca Vitamin B12 Folate Epstein-Barr virus titer BUN Creatinine egfr Neurologic Disease For contrast dye

6 Test What is it? Low Value High Value WBC Total # WBCs (lymphocytes, monocytes, neutrophils, eosinophils, basophils), which defend the body against infection Autoimmune diseases, immunosuppression, bone marrow failure, chemotherapy, viral infections RBC Total RBCs, which pick up oxygen from the blood and deliver it to tissues throughout the body Iron, vitamin B12, or folate deficiency, bone marrow damage, leukemia or lymphoma; acute/chronic blood loss; RBC hemolysis HCB Oxygen-carrying pigment in RBCs See RBC See RBC HCT RBC % See RBC See RBC Infection, inflammation, leukemia, intense exercise, corticosteroids Dehydration, renal problems, pulmonary disease, congenital heart disease, polycythemia vera MCV Average size of RBCs Iron deficiency Vitamin B12 or folate deficiency MCH Amount of HGB per RBC Iron deficiency Vit B12 or folate deficiency MCHC Average concentration of HGB in a given volume of RBCs Iron deficiency Sickle cell disease, hereditary spherocytosis PLT # of platelets, which are important for blood clotting Bone marrow failure, chemotherapy, viral infections, lupus, pernicious anemia, leukemia or lymphoma, sequestration in the spleen, certain medications Leukemia, myeloproliferative disorders, inflammatory conditions RDW/RDW- SD Measurement of the variation in RBC size Iron deficiency, B12 or folate deficiency, recent blood loss MPV Average volume of a platelet Aplastic anemia, thrombocytopenia Certain inherited disorders GRAN LYMPH MONO EOSINO BASO IMMATURE GRAN # or % of WBCs with granules in their cytoplasm # or % of lymphocytes, which are WBCs that include B-cells, T-cells, and natural killer cells # or % of monocytes, which are WBCs that move out of the circulating blood and into the tissue, where they mature into macrophages # or % of eosinophils, which combat parasitic infections and are involved in asthma or allergy responses # or % of basophils, which are involved in allergy responses WBCs that will become monocytes, eosinophils, and basophils Immunosuppression, bone marrow failure, chemotherapy Immunosuppression, -AIDS, bone marrow failure, chemotherapy Immunosuppression, bone marrow failure, chemotherapy Infection, inflammation, leukemia, intense exercise, stress, corticosteroids Viral infections, leukemia, lymphoma Chronic infections, autoimmune diseases, leukemia Parasitic infections Active allergy response Serious infections, leukemia, severe body stress