Med Chem 535P ~ Diagnostic Medicinal Chemistry. General Comments

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1 Med Chem 535P ~ Diagnostic Medicinal Chemistry General Comments Most blood chemistry and serology assays are performed automatically. Larger clinical laboratories often use sophisticated analyzers that can run 12 different tests on a blood sample and do one test per second. Point of Care Testing (PC) is now done at the bedside, in clinics and physician s offices, etc. These are typically used for screening and in some cases monitoring to guide therapy (IR), but are not used as a diagnostic test. PC tests are performed using smaller, less costly instruments and include blood chemistries, ABGs, coagulation tests, microbiology, and MI injury markers. Home Tests are now available for many of the common screening and monitoring tests. They include collection kits, where the patient collects a sample and mails to a central lab for analysis (occult blood, cholesterol, and TSH) and complete tests, where the patient performs the complete analysis (glucose, ovulation, pregnancy, even HIV ).

2 Screening tests are performed on healthy individual to detect disease at an early stage. They are quick, inexpensive, and reliable but do not provide a definitive answer. Examples include chemistry panel, lipid profile, TB skin test, fecal occult blood. Diagnostic tests are performed on at-risk individuals. They are used to confirm a suspected diagnosis. Remember, all lab results must be evaluated in the context of all other clinical evidence; lab errors, sample handling errors, general trends, patient-specific factors, etc. Some Terminology Analyte ~ the compound that is of interest in the analytic test Accuracy ~ how close is the measured value to the actual value Precision ~ how reproducible is the measurement Sensitivity ~ how good is the test at actually detecting the sample when it truly exists (minimal false negatives) Specificity ~ how good is the test at detecting only the desired sample (minimal false positives) Qualitative test ~ the result is reported as a yes or no result only Quantitative test ~ the result reports an exact numerical value Reference Range ~ a statistically derived numerical range of values that is typical in a normal individual. This is derived by testing a sample population and determining the mean and standard deviation of the measurement. ote that the reference range may show significant physiological variation (age, gender, ethnicity, etc.) and may vary from lab to lab.

3 Diagnostic Assays Spectroscopy (absorbance and fluorescence) ~ direct vs. indirect F e I I F e o r t h o - p h e n a n t h r o l i n e F e r r o u s t r i s - o - p h e n a n t h r o l i n e orange-red Coupled Enzyme Assays ~ typically measured spectrophotometrically. - H 3 + aspartate transaminase H 3 + aspartate α-ketoglutarate oxaloacetate glutamate malate dehydrogenase ADH + H + AD + - H - AD + in blue; ADH in red malate Agglutination Enzyme Linked ImmunoSorbant Assay (ELISA)

4 Flow Cytometry

5 Lab Values You Will eed to Know (i.e., memorize): Chem-7 a + K + Cl - HC 3 - BU Scr Glucose Chem-10 ABG Lipid Panel CBC w/ Dif Absolute eutrophil Count (AC) Serum Proteins/Enzymes Blood Sugar Lipids plus Ca 2+, Mg 2+, phosphorous Arterial ph, HC 3 -, p 2, pc 2 Base Excess (B.E.) Arterial oxygen saturation (Sa 2 ) Triglycerides Total Cholesterol LDL RBC, WBC, platelets Hb, Hct eutrophils, eutrophils absolute (AC) Eosinophils, Eosinophils absolute Basophils, Basophils absolute Lymphocytes, Lymphocytes absolute Monocytes, Monocytes absolute Total Protein Albumin International ormalized Ratio (IR) Prothrombin Time (PT) Alanine transaminase (ALT) Aspartate aminotransferase (AST) Serum bilirubin Urine bilirubin Glucose Triglycerides Total Cholesterol LDL

6 Study Guide Terms You eed to Know Accuracy Analyte egative control Positive control Precision Qualitative test Quantitative test Reference Range Semi-Quantitative test Sensitivity (false negatives) Specificity (false positives) You should be prepared to describe the difference between a clinical lab, a point of care test, and a home test. You should be prepared to contrast home collection and mail vs. complete home test. Be prepared to describe the difference between a Screening test and a Diagnostic test. How are they used? Lab values that you need to memorize will be indicated throughout the course. For all lab values discussed in class throughout the quarter, be prepared to recognize a patient lab value that is out of the range and why it is relevant to diagnosing a clinical problem and/or monitoring a therapeutic outcome.