Recap of Monday's LIVE Study Session · Microscope Views (FREE)

Recap of Monday's LIVE Study Session

Greetings Gang 😈🤪

HERE IS THE RECAP OF MONDAY'S LIVE STUDY SESSION

‼️✨There is another one tomorrow evening at 3PM PST/4PM MST/5PM CST/6PM EST

Meeting Purpose

Review ASCP practice questions across multiple lab disciplines.

Key Takeaways

Lewis Antigens are Adsorbed: Lewis antigens are unique because they are not intrinsic to RBCs; they are passively adsorbed from plasma. This key distinction from other blood groups is a common exam point.
Yersinia enterocolitica is a Transfusion Risk: This organism's ability to grow at 4°C (blood storage temperature) makes it a critical cause of transfusion-related septicemia, a high-yield exam fact.
MDS Cytopenia is from Apoptosis: Myelodysplastic Syndromes (MDS) cause low cell counts (cytopenia) because the bone marrow produces abnormal cells that are destroyed via apoptosis before they can be released into circulation.
PCR Steps are Denaturation, Annealing, Extension (DAE): This is the correct sequence for PCR. "Hot start" methods prevent non-specific reactions by keeping the polymerase inactive until the optimal temperature is reached.

Topics

Molecular Biology & Genetics

DNA Nucleotide Composition:A DNA nucleotide consists of deoxyribose, phosphate, and a nitrogenous base (A, T, C, or G).Ribose and Uracil (U) are components of RNA only.
Huntington's Disease:Caused by a trinucleotide repeat: CAG.CGG is associated with Fragile X syndrome.
Second Messengers (cAMP vs. cGMP):cAMP is generated from ATP by adenyl cyclase.cGMP is generated from GTP by guanylyl cyclase.Clinical Relevance:cGMP → Blood vessel relaxation (vasodilation), explaining the action of drugs like nitroglycerin and .cAMP → Bronchodilation, explaining the action of drugs like albuterol.Lab Takeaway: High hormone levels with no expected effect can indicate a signal transduction problem (e.g., Type 2 Diabetes), not a hormone production issue.
PCR Steps & Hot Start PCR:Standard PCR Sequence: Denaturation → Annealing → Extension (DAE).Hot Start PCR: Prevents non-specific reactions by keeping the polymerase inactive until the optimal temperature is reached.Methods:Keeping the reaction on ice until the thermal cycler heats.Separating polymerase and primers with a wax bead that melts at high temperature.Using modified polymerases that are only activated at high temperatures.
MALDI-TOF Mass Spectrometry:Mechanism: Identifies bacteria by measuring the mass-to-charge ratio of molecules.Process: A laser vaporizes the sample, and the "time of flight" of the molecules is compared to a database for identification.Key Point: The laser does not amplify bacteria; it vaporizes them.

Hematology & Coagulation

Bone Marrow Cellularity:Highest in young children and decreases with age.The myeloid-to-erythroid (M:E) ratio is normally 1.5:1 to 3:1.As we age, fat increases and hematopoietic tissue decreases.
Lewis Blood Group System:Key Fact: Lewis antigens are not structural components of the RBC membrane.They are passively adsorbed from plasma, and their expression is influenced by secretor status.
Myelodysplastic Syndromes (MDS):Cause of Cytopenia: Excess apoptosis (programmed cell death) of abnormal, dysplastic cells in the bone marrow.This destruction prevents cells from being released into circulation, leading to low counts.
Heparin Monitoring:Unfractionated Heparin is monitored with the PTT (measures intrinsic and common pathways).Warfarin (Coumadin) is monitored with the PT/INR (measures extrinsic and common pathways).

Microbiology & Parasitology

Yersinia enterocolitica:Key Fact: A cryophilic organism that can grow at 4°C.Clinical Significance: A potential cause of transfusion-related septicemia because it can replicate in refrigerated blood products.
Simmons Citrate Agar:Positive Result (Blue Color): Caused by the production of ammonia from ammonium phosphate, which raises the pH.Mechanism: Bacteria use sodium citrate as a carbon source, but the resulting pH shift is insufficient for the color change. The ammonia production is the direct cause.
Trichrome Stain:Primary Use: Identifying intestinal protozoa (e.g., Entamoeba histolytica, Giardia) due to their small size.Wet Mounts: Used for larger parasites like nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes).

Blood Bank & Transfusion Medicine

Leukocyte-Reduced Apheresis Platelets:QC Requirement: Must contain a maximum of 5 x 10^6 residual WBCs.Rationale: To reduce the risk of HLA sensitization, graft-versus-host disease, and other transfusion complications.Other QC Values:Apheresis granulocyte unit: ≥1 x 10^10 WBCs.Apheresis platelet unit: ≥3 x 10^11 platelets.Random donor platelet unit: ≥5.5 x 10^10 platelets in 90% of units tested.
Storage Lesion in RBCs:Biochemical Changes During Storage:Decreases: Plasma pH (due to lactic acid), glucose, ionized calcium, folate.Increases: Plasma potassium, free hemoglobin (from hemolysis), ALT, AST, creatinine.Clinical Significance: Explains why samples have stability limits and why delayed processing affects certain test results.

Lab Operations & Safety

Specimen Collection for Serum:Tube of Choice: Red-top tube or gold-top (SST).Mechanism: These tubes allow the blood to clot, separating the serum (plasma without clotting factors) from the cells.
Lab Personnel Competency Oversight:Directly Responsible: CAP and The Joint Commission (TJC).Indirectly Responsible: HCFA (now CMS) enforces competency by tying compliance to Medicare/Medicaid reimbursement.Not Responsible: CLSI provides standards but has no regulatory authority.
Engineering Controls vs. PPE:Engineering Controls: Devices that isolate the worker from a hazard (e.g., sharps container, biosafety cabinet).PPE: Personal protective equipment that protects the worker (e.g., lab coat, gloves, face shield).

General Lab Math & Statistics

Microliter Conversion:1 microliter (µL) = 0.001 mL = 1 x 10^-6 L.
Celsius to Fahrenheit Conversion:Formula: F = (C x 9/5) + 32.
Standard Deviation (SD) & Normal Distribution:1 SD: Encompasses 68% of results.2 SD: Encompasses 95% of results.3 SD: Encompasses 99.7% of results.