Diagnostic Methods & Technologies Flashcards

In flow cytometry, side scatter (SSC) mainly reflects which cellular property?

Answer: Internal complexity or granularity

Side scatter is light deflected at about 90° by internal structures, so granulocytes show high SSC.

In an impedance (Coulter principle) cell counter, the height of each voltage pulse is proportional to which property?

Answer: Cell volume

A cell passing through the aperture displaces conductive fluid, and the size of the resistance change matches the cell's volume.

Which CD marker is enumerated by flow cytometry to assess hematopoietic progenitor cell yield before stem cell transplant?

Answer: CD34

CD34 is the standard marker for hematopoietic stem and progenitor cells, usually counted with the ISHAGE gating protocol.

Which technology lets newborn screening labs measure amino acids and acylcarnitines together from a single dried blood spot?

Answer: Tandem mass spectrometry (MS/MS)

MS/MS can quantify dozens of metabolites in one run, which allows panels for amino acid, fatty acid oxidation, and organic acid disorders.

A peritoneal dialysis patient using icodextrin has a falsely elevated point-of-care glucose. Which strip chemistry is most likely responsible?

Answer: Glucose dehydrogenase with PQQ cofactor

GDH-PQQ is not specific for glucose and also reacts with maltose, which forms when icodextrin is metabolized, so results read falsely high.

The Clark electrode in a blood gas analyzer measures pO2 by which principle?

Answer: Amperometry, using the current from oxygen reduction at a platinum cathode

Oxygen diffuses through a membrane and is reduced at a polarized platinum cathode, and the current produced is proportional to pO2.

Which HbA1c method measures all glycated hemoglobin and is least affected by common hemoglobin variants such as HbS or HbC?

Answer: Boronate affinity chromatography

Boronate binds the cis-diol groups of glycated hemoglobin regardless of charge, so structural variants interfere very little.