My Missed LabCE Questions

Which of the following tests confirms the presence of Bence-Jones proteinuria?

• Protein electrophoresis

• Sulfosalicylic acid precipitation

• Cryoprecipitation

• Immunoelectrophoresis

Answer explanation

Immunoelectrophoresis is used to detect the presence of Bence-Jones proteins. Immunoelectrophoresis is used to help detect, diagnose, and monitor the course and treatment of conditions associated with abnormal proteins (such as Bence-Jones), including Multiple Myeloma, Waldenstrom's macroglobinemia, and a few other related diseases.

What species of Candida accounts for around 20% of urinary yeast isolates?

• Candida albicans

• Candida glabrata

• Candida krusei

• Candida tropicalis

Answer explanation

Candida glabrata is the second most common Candida species to cause disease (Candida albicans is the most common). In urinary yeast isolates, it is identified about 20% of the time. Infections tend to be aggressive and difficult to treat with traditional antifungal therapy. It has different sugar assimilation patterns than Candida albicans, notably rapid assimilation of trehalose, so it can easily be differentiated.

Candida krusei and Candida tropicalis are seen in immunocompromised patients and cause nosocomial infections.

Which malarial species schizont that typically contains 6-12 merozoites with a central brown/green pigmented mass and sometimes forms rosette shapes is found inside RBCs?

• Plasmodium vivax schizont

• Plasmodium ovale schizont

• Plasmodium malariae schizont

• Plasmodium falciparum schizont

Answer explanation

Plasmodium malariae schizont is the correct answer. The number and the arrangement of merozoites aid in distinguishing the Plasmodium species schizonts. the schizonts of Plasmodium malariae are the only ones that typically contain 6-12 merozoites with large nuclei clustered around a mass of dark-brown/green pigment with the occasional rosette forms. Plasmodium malariae is known to infect older cells, which are smaller than normal.

Plasmodium vivax schizont is incorrect because this produces 12-24 merozoites in the schizont with amoeboid trophozoites that have bizarre, irregular shapes. It infects reticulocytes, which will be larger than normal cells.

Plasmodium ovale schizont is incorrect because it produces 4-12 merozoites in the schizont and the RBCs exhibit ragged or jagged margins. It also infects reticulocytes.

Plasmodium falciparum schizont is incorrect because it produces 8-36 merozoites in the schizont, has multiple ring forms, and produces crescent or banana-shaped gametocytes inside the RBCs.

All of the following factors would cause an increase in ESR (erythrocyte sedimentation rate) values except

• Severe anemia

• Abnormal proteins (rouleaux)

• Blood drawn in sodium citrate anticoagulant

• Slanted tube (not perpendicular)

Answer explanation

Either EDTA or sodium citrate are used for ESR testing since neither will affect the ESR value.

Severe anemia and abnormal proteins (rouleaux) can cause increased ESR value.

A slanted tube can accelerate sedimentation rate by 30%.

A specimen without any additives or anticoagulant should be allowed to clot for _____ before centrifugation.

• 5 minutes

• 30 minutes

• 3 hours

• 2 hours

Answer explanation

Incomplete clotting will leave small fibrin residue in the serum which can interfere with testing or clog the probes and/or tubing. It should not be held for over 2 hours due to sample integrity. Certain tests can be falsely increased (like potassium due to hemolysis) or decreased (like glucose due to cellular consumption)

What is the first stage of the Wucheria bancrofti life cycle in human infections?

• The infective stage develops in insect

• Ingested by blood-sucking insect

• Mature in circulatory system, body cavity, or connective tissue in humans

• Microfilariae in blood or skin of humans

Answer explanation

Intermediate host: mosquito

Definitive hose and reservoir: humans

First step: Microfilariae in blood/skin of humans

Second step: Ingested by blood-sucking insect

Third step: infective stage develops in insect

Fourth step: enter humans when insect takes blood meal

Fifth step: mature in circulatory system, body cavity, or connective tissue in human

Final step: adult worm

The bacterial species growing on the surface of the MacConkey agar plate shown in the photo, a coccobacillary non-fermenter and common cause of nosocomial hospital-acquired pneumonia, can be presumptively IDed as:

• Burkholderia cepacia

• Moraxella catarrhalis

• Acinetobacter baumanii

• Neisseria lactamica

Answer explanation

Acinetobacter baumanii: non-lactose fermenting, Gram-neg cocobacillus, produce purplish hue pigment on MAC agar, considered one of the most frequent cause of hospital-acquired pneumonia

Burkholderia cepacia: can cause pulmonary infections, particularly in cystic fibrosis patients, NOT a coccobacillus, does not produce purplish hue

Moraxella catarrhlis: diplococcus, resembles Acinetobacter baumanii on gram stain, cause respiratory infections in patients w/ pulmonary disease or chronic bronchitis, does NOT grow on MAC agar, not considered hospital-acquired

Neisseria lactamica: gram-neg diplococcus, does NOT grow on MAC agar, not associated with respiratory infection, not associated with hospital-acquired infections

According to Westgard and CLIA, how many specimens should be run by each method on the same day for 8-20 days to compare a test method with a comparative method?

• 20-40

• 40-100

• 100-150

• >150

Answer explanation

To compare a test method with a comparative method, it is recommended by Westgard and CLIA that 40-100 specimens be run by each method on the same day over 8-20 days (preferably within 4 hours), with specimens spanning the clinical range and representing a diversity of pathologic conditions.

A patient with an infectious mononucleosis infection presents in the ER. Physicians order a spinal tap, which is immediately sent to the lab for review. What is the cell in the photo?

• Monocyte

• Macrophage

• Mesothelial Cell

• Reactive Lymphocyte

Answer explanation

Reactive lymphocytes are commonly found in certain viral infections, especially infectious mononucleosis. Notice the larger size nd abundant cytoplasm. There is also apparent vacuolization, which is a key feature of atypical/reactive lymphocytes. The chromatin pattern of this cell, plus the shape, color, and size rules out the other choices.

When flammable chemicals/grease are involved, what is the appropriate fire designation?

• Class A

• Class B

• Class C

• Class D

Answer explanation

Class A fires: paper, wood, cloth

Class B: flammable liquids (grease, chemicals, gasoline, oil)

Class C: electricity

Class D: combustible/reactive metals