CLSC 410 MODULE 1 BEST SET EXAM 2025

Accuracy - -how close the result is to the true value Precision - -how close multiple results are to each other In a clinical setting we strive for. . . - -- both accuracy and precision - but this is a balancing act because one can never be both 100% accurate and precise Analytical Sensitivity - -ability of method to detect the smallest amount of a substance Analytical Specificity - -ability of method to detect only what you are assaying = minimal interference! What is a reference interval/What is it used for ? - -- a range of values from a reference population - used for comparison of results - not everyone is going to fall within this range; those that don't are indicated as being sick - the range is specific to the method The 5 Rules for Rounding - - 1. Express molecular weight in whole numbers 2. if the value 5, leave it 3. if the value 5, increase by one 4. if the value = 5: leave it if the proceeding number is even; increase by one if the proceeding number is odd 5. ONLY ROUND AT FINAL STEP Metric system units - -n = 10⁻⁹ µ = 10⁻⁶ m = 10⁻³ c = 10⁻² d = 10⁻¹ k = 10³ 1 dL = 100 mL Celsius --- Fahrenheit - -(C * 1.8) + 32 = F Fahrenheit --- Celsius - -(F − 32) * 0.556 = C CLSC 410 CLSC 410 Fahrenheit --- kelvin - -1. convert from Fahrenheit to Celsius 2. Add 273 Module 2 - - Simple dilutions = - -(sample volume) ÷ (sample volume + diluent volume) Quantity sufficient (QS) rule - -- add sufficient amount of diluent to get the total volume - always include when question asks HOW to do/make a sample To find the new concentration from a diluted sample such as in serial dilution problems . . . - -- dilution x concentration = new concentration - always assume the calibrator (standard) isn't diluted, unless stated otherwise Hydrates - -- often used to make up solutions - occur when water molecule is attached to a salt - so when dealing with them, you must account for the water molecule = set up a ratio to convert from hydrates to anhydrous Specific Gravity - -- the weight of a solid/liquid ÷ the weight of an equal volume of water expressed as per mL - 1 mL of water = mass of 1 g - used in making solutions of concentrated chemicals; use along with the purity to determine the amount of substance/volume. Percentage Solutions - -1. Weight/volume (w/v): used when solute is mixed with solvent; ex: 15% NaCl = 15 g NaCl and qs to 100 mL with diluent 2. Volume/volume (v/v): liquid in a liquid solvent; ex: 10% ethanol = 10 mL of ethanol and qs to 100 mL with diluent Ex simple dilution problem: A procedure calls for a 1/250 dilution of urine. Keeping the total volume to 5 mL, how would you dilute the specimen? - -1. Set up a ratio: X/5 = 1/250; 2. Cross multiply: 250X = 5 3. x = 0.02, but you need to say HOW: Take 0.02 mL of specimen urine (20 µL) and qs to 5 mL (add 4.98 mL) with diluent. Ex dilution problem #2: You are performing a urine glucose. The procedure calls for a 1/5 dilution but you made a 1/10. Then the procedure requires 0.3 mL but you used 0.1 mL. The glucose value is 60 mg/dL.What should be reported out? - -1. You can start with the result and set up a simple ratio to find out what the result would be if you used the correct volume: [0.1/60] = [0.3/X] (0.3) x (60) = (X) x (0.1); X = 180 mg/dL OF THE 1/10 DILUTION 2. Find the factor difference between the two ratios 1/10 and 1/5: (1/10) / (1/2) = 1/5; so factor is 1/2 CLSC 410 CLSC 410 3. Divide 180 mg/dL by 1/2 to get the true concentration Answer: 360 mg/dL of glucose should be reported out. Ex calibrator dilution problem: You are given a 500 mg/dL glucose stock standard. How would you make 1.0 mL of a 25 mg/dL standard? - -1. Use the equation: C1V1 = C2V2 2. [1.0 mL] × [25 mg/dL] = [V2] × [500 mg/dL] 3. V2 = 0.05 mL = 50 µL Answer: measure 0.05 mL (50 µL) of the 500 mg/dL glucose stock solution and qs to 1.0 mL (add 0.95 mL (950 µL)) with diluent. Ex hydrate problem: How many grams of CaCl2 .3H2O are needed to make 500 mL of 10% w/v CaCl2? (Round off to the tenth.) (MW of CaCl2 = 110; MW of CaCl2 .3H20 = 164) - -1. 10% w/v CaCl2 in 500 mL means that the weight of CaCl2 is 10% of the 500 mL solution = 50 g 2. Set up a ratio using the MWs and cross multiply: 110/164 = 50/x x = 74.5 g Answer: weigh 74.5 g of CaCl2 .3H2O and qs to 500 mL with diluent. Ex specific gravity problem: 500 mL conc. H2SO4 (sp. gravity 1.8; 95% purity) is placed in a final volume of 750 mL.What is the solution's molarity?(Round off to tenth.) - -1. 1.8 x 0.95 = 1.71 g H2SO4 / mL of solution = 1710 g/L 2. 1710÷98 (MW of H2SO4) = 17.4M H2SO4 3. Set up C1V1 = C2V2 to find final concentration: (17.4M H2SO4)(500 mL) = (x)(750 mL) 4. x = 11.6M H2SO4 Ex solution problem: Given a patient serum having a glucose of 125 mg/dL, and a 1000 mg/dL glucose standard, how would you make a 300 mg/dL sample for a linearity study? - -1. For these problems set up/use the equation V1C1 + V2C2 = VFCF C1 = 125 C2 = 1000 CF = 300 V1 = 5 mL (you can pretty much just choose a volume, but 5 is easy to work with and reasonable) 2. Plug in and solve the equation to find V2: [5][125] + 1000V2 = 300[V1 + V2] 625 + 1000V2 = 1500 + 300V2 1000V2 = 875 + 300V2 700V2 = 875 V2 = 1.25 mL Answer (have to write it out because question asks "how"): Take 5 mL of the patient serum glucose of 125 mg/dL and add it to 1.25 mL of the 1000 mg/dL glucose standard, to produce 6.25 mL of the 300 mg/dL glucose concentration. CLSC 410 CLSC 410 Module 3 - - A mole = - -g/MW Molarity (M) = - -g/L ÷ MW - can also be expressed as mol/L or mmol/mL (used most often in clinical lab) Normality - -- similar to molarity, except based on eq weight, not MW 1 N of a solution = 1 Eq/L N = [g/L÷MW] × valence Eq Weight = - -MW ÷ valence Valence - -- the total positive charge/number of combinable H⁺ ex: H₂SO₄ = 2 H₃PO₄ = 3 HCl = 1 NaCl = 1 mEq/L - -- use in a clinical lab - = [mg/L]÷eq wt = [mg/L]÷[MW/valence] = [[mg/L]÷MW]×valence Converting Molarity to Normality - -- N = same number or larger than M N = M × valence OR M = N ÷ valence Converting mEq/L to mmol/L and mg/dL - -mEq/L = [[mg/L[÷MW] x valence mEq/L = [mmol/L] × valence Ex conversion problem: Convert 180 mg/dL glucose to mmol/L. Reference interval for glucose is 3.6 - 6.1 mmol/L.(MW of glucose = 180) - -1. Convert dL to L (multiply by factor of 10): 180 mg/dL = 1800 mg/L 2. Convert mg to mmoles (divide by the MW): [1800 mg/L] ÷ 180 = 10 mmol/L Ex conversion prob #2: Convert 0.5 mmol/L PO4-3 to mg/dL. Reference interval is 3.0 - 4.5 mg/dL. (MWPO4 = 95) - -1. Convert L to dL (divide by factor of 10): 0.5 mmol/L = 0.05 mmol/dL 2. Convert mmoles to mg (multiply by the MW): 0.05 x 95 = 4.8 mg/dL Ex problem #3: How would you make 100 mL of an 80 mmol/L Cl- standard? The stock shelf has NaCl crystals .(MW of Cl-=35;MW of Na+ = 23) - -1. Convert 80 mmol/L to mg/dL (because 100 mL = 0.1L) by multiplying by the MW of Cl: [80 x 35] ÷10 = 280 mg/dL 2. Set up a ratio to correct for tthe weight of sodium in NaCl and find the correct concentration: 35/58 = 280/X; X = 464 mg CLSC 410 CLSC 410 Answer: Weigh 464 mg (0.464 g) of NaCl stock crystals and qs to 100 mL with diluent. Module 4 - - Absorbance = - -2 − Log%T OR ∈bC = Beer's Law! Absorbance is - -- linear to concentration - most accurate between 0.2-0.8 Transmittance is - -inversely proportional to concentration Variables of Beer's Law - -∈ = molar absorptivity (a constant) b = pathlength (of the cuvet) C = concentration Characteristics of Calibrators/Standards - -1. pure 2. weighed out 3. has a known concentration, because it's weighed out Types of Calibrators - -1. Primary: exact known C; purity 99.8%; expensive 2. Secondary: pure, but less than primary; used in lab Which chemical grade do we use in lab? - -Reagent/analytical grade = highest degree of purity certified by ACS Clinical Lab Reagent Water (CLRW) - -- replaces type 1 & 2 - AKA D.I. Water - used in methods that require minimal interference and max precision - requires purifiers - check quality mainly by measuring resistivity and presence of bacteria Calculating Concentration of Unknown (Using spectroscopy) - -[ Absorbance of unknown ÷ absorbance of standard] × concentration of standard - REMEMBER: Subtract any blank measurements from sample absorbance values to obtain the corrected absorbance values! Calibration Curve - -- used to determine if assay follow