Immunohematology Laboratory Review: ABO Grouping, D Status, Secretor Determination, RCS Preparation, and Lab Safety

Comprehensive practice flashcards covering ABO blood grouping, Rh D status determination, secretor testing, red cell suspension preparation, and laboratory safety protocols.

In ABO blood grouping, what are the unknown component and reagent used in forward typing versus reverse typing?

In forward typing, the unknown is the red cell antigen and the reagent is commercial antisera. In reverse typing, the unknown is antibodies and the reagent is known cells.

What are the specific centrifugation parameters for the ABO forward tube method?

Centrifuge for $15\,\text{seconds}$ at $3,400\,\text{rpm}$.

What cell suspension concentration and incubation conditions are required for ABO forward grouping using Gel Technology?

A $2\text{--}5\%$ red blood cell suspension is prepared, reagents and samples must be at room temperature ($18\text{--}25^\circ\text{C}$), and the gel card is centrifuged at $2000\,\text{rpm}$ for $10\,\text{minutes}$.

How are the tube reaction results interpreted in ABO reverse grouping?

Type O shows no reaction/agglutination with Type A and B cells; Type A agglutinates Type B RBCs; Type B agglutinates Type A RBCs; Type AB shows no reaction with both RBCs.

What are the primary disadvantages of the slide method for ABO grouping compared to the tube method and gel technology?

The slide method puts the medical technologist at greater risk of contact with the specimen, is more prone to drying, is not suitable for detecting ABO antibodies in serum/plasma, and is less accurate.

What are the characteristics and routine testing requirements of the Rh D antigen?

The D antigen is a non-glycosylated protein on the red cell membrane, highly immunogenic, and the most clinically significant non-ABO antigen. It is the only Rh antigen that undergoes routine testing.

What are the three mechanisms responsible for the occurrence of the $D^u$ (weak D) phenotype?

1. Genetic Weak D / Genetic $D^u$ / Low grade $D^u$ (inherited reduced expression with complete but few antigens); 2. C Trans / Position effect / Gene Interaction Effect (allele carrying D is trans to an allele carrying C, e.g., DCe/dCe); 3. D mosaic antigen (missing components of D antigen subunits).

How is D status interpreted based on Anti-D and Indirect AHG testing results?

If Anti-D is $+$, the interpretation is Rh positive. If Anti-D is $-$ and Indirect AHG is $+$, it is Rh positive. If Anti-D is $-$ and Indirect AHG is $-$, it is Rh negative.

What antibody specificity is produced by Rh null individuals, and what clinical symptoms characterize Rh Null Syndrome?

Rh null individuals express no Rh antigens ($-\text{/}-$) and can produce Anti-Rh:29 (anti-total Rh). Symptoms include stomatocytosis, reticulocytosis, compensated hemolytic anemia, increased HbF and bilirubin, decreased haptoglobin and OFT, and slightly decreased Hb and Hct.

What is the most common cause of Rh-typing ($D^u$ typing) discrepancies, and how should cold agglutinins be addressed?

Positive DAT is the most common cause. For cold agglutinins, the patient sample should be warmed to $37^\circ\text{C}$ and immediately retested.

What is the specimen concentration and viewing temperature required for the Rh typing slide method procedure?

Requires a $40\text{--}50\%$ suspension of RBCs and an optimum viewing temperature of $37^\circ\text{C}$ on a viewing box.

What defines a secretor, and what laboratory reaction phenomenon forms the basis of secretor status testing?

Secretors are individuals who express ABH blood group substances in soluble forms in secretions like saliva. Testing relies on hemagglutination-inhibition (neutralization), where soluble antigens neutralize antibodies to inhibit agglutination.

What initial preparation steps are performed on raw saliva for secretor status determination?

Collect $2\,\text{mL}$ saliva, place in a water bath for $10\,\text{mins}$, centrifuge at $3400\,\text{rpm}$ for $10\,\text{mins}$, transfer supernatant, and make a $1:2$ dilution of the supernatant with NSS.

What incubation options are available after mixing diluted antisera, saliva supernatant, and RBCs in secretor testing?

Incubate at room temperature for $30\text{--}60\,\text{mins}$ OR at $37^\circ\text{C}$ for $15\,\text{mins}$.

What result indicates a POSITIVE secretor status, and what is its significance and resolution?

A POSITIVE secretor test shows an absence of agglutination because soluble ABH antigens neutralized the diluted antiserum. Secretor substances can cause ABO discrepancies, resolved by washing red cell samples with NSS.

What is the optimal concentration range, pH, and appearance of Normal Saline Solution (NSS) used in RBC suspension preparation?

NSS contains $0.85\%\text{--}0.9\%$ NaCl, has a pH of $7.0\text{--}7.4$, and a properly prepared red cell suspension has a characteristic TOMATO RED COLOR.

What is the procedure for preparing washed packed red blood cells (WPRBC)?

Pipette $3\,\text{mL}$ whole blood, fill tube with NSS, cover with Nescofilm and mix, centrifuge for $5\,\text{mins}$ at $3400\,\text{RPM}$, decant supernatant using a Pasteur pipette, and repeat the washing steps $2$ more times.

If $0.15\,\text{mL}$ of WPRBC is used to prepare a $5\%$ red cell suspension, what is the required volume of NSS?

Total Volume $\text{TV} = \frac{0.15}{5} \times 100 = 3\,\text{mL}$. Required $\text{NSS} = \text{TV} - \text{WPRBC} = 3 - 0.15 = 2.85\,\text{mL}$.

What is the correct sequence for DONNING Personal Protective Equipment (PPE)?

1. Laboratory coat/gown, 2. Mask or respirator, 3. Goggles or face shields, 4. Gloves.

What is the correct sequence for DOFFING Personal Protective Equipment (PPE)?

1. Gloves, 2. Goggles or face shields, 3. Laboratory coat/gown, 4. Mask or respirator.

What are the step-by-step procedures and required contact time for decontaminating a biological spill in the laboratory?

1. Notify other workers; 2. Wear shoe covers and safety goggles; 3. Put on gloves and cover spill with paper towels; 4. Pour disinfectant over towels from edges to center; 5. Decontaminate all objects in spill area; 6. Allow $30\,\text{mins}$ of contact time.