Working With Arboviral Specimens

Jan. 9, 2023

This video is a clinical diagnostics training module on reagent dilutions and optimization of the CDC Arboviral IgM antibody capture enzyme-linked immunosorbent assay (CDC Arboviral MAC-ELISA).

Detecting Arbovirus IgM Antibodies in Clinical Serum Samples

The training consists of 3 sections with knowledge checks at the end of each section. Below are some key takeaways and timestamps from each section.

Part 1: How to Make Single and Serial Reagent Dilutions

Making dilutions is a technique that reduces the concentration of solutions in an accurate and systematic way. A concentrated stock solution is the solution from which you are starting, and the working dilution describes the resulting diluted solution that is used in your assay. The solute is the substance being diluted, and the diluent is the substance that the solute is being diluted with. 

A serial dilution, also known as a dilution series, involves making multiple dilutions with sequentially decreasing concentrations. Typically, the dilution factor remains constant for each dilution in a series, resulting in an exponential decrease in concentration of the solute. 
  • Single/Serial Dilutions Overview[0:59].
  • ​How Dilutions are Expressed [2:08].
  • Understanding the Math [3:20].
  • How to Make Dilutions [6:36].
  • How to Make a Dilution Series [7:32].

Part 2: Optimizing the CDC Arboviral MAC-ELISA

Sometimes the CDC Arboviral MAC-ELISA needs to be optimized. Examples include:
  • When there is a reduction in the dynamic range (difference between the highest to lowest optical density) of the test [10:10].
  • There is an excessive change in assay control values [11:20].
  • There are new reagent lots [12:30].
  • Test performance is evaluated [13:24].
  • Troubleshooting fails to identify problems with this assay [14:27]. 
  • Part 3: Titrating Reagents for the CDC Arboviral MAC-ELISA

Titration can be used to determine a reagent concentration or dilution, when changing a new reagent lot, for yearly standardizations, for developing novel assays or when multiple failed tests occur, despite troubleshooting.

The titration is a 3-day assay. You will need sufficient material to include assay controls on the plate. Except for the reagent being titrated, keep all reagents at their current working dilutions. 
  • Single Antigen Titration [16:49].
  • Box Titration [23:56].

How to Ship Entomological Specimens for Arbovirus Testing

In this video, we will cover steps needed to ship specimens to the Centers for Disease Control and Prevention (CDC). CDC offers mosquito and tick pool testing to local, state and territorial health departments. Shipping samples like mosquito or tick pools to a testing facility may sound like a simple thing, but how you prepare samples could determine how quickly you get results.

Any time and energy that the testing lab has to spend manipulating specimens that have been improperly labeled or packaged is time that could have been spent testing them. Packages that are labeled, packaged and shipped correctly can be incorporated into the testing workflow quickly and efficiently, which means a faster return on results for you. Below are some key takeaways and timestamps from the video.

Preparing Sample Tubes

Before shipping samples to a laboratory for testing its important to find out what kind of homogenizing tubes will fit in their instruments. Then follow one of the recommended options for labeling.
  • Use the appropriate tubes [1:08].
  • Use the appropriate labels [1:45].

Preparing Sample Boxes

Place tubes in numerical order in an appropriate box. This could be a white cardboard freezer box with dividers or a plastic tube box. Do not put loose tubes in a plastic bag. 
  • Use a box with dividers [2:36].
  • Label clearly; the lab processing your specimens receives many shipments, so details help. [3:40].

Preparing Shipping Boxes

If you are shipping multiple boxes, place the boxes into a -80C or -20C freezer until you're ready to ship them. Use a shipping container specifically designed to ship cold materials. Place the appropriate amount of blue ice packs or dry ice into the bottom of the container. The amount of ice you will need may depend on weather conditions. 
  • If you use dry ice, be sure to follow federal guidelines and label your containers appropriately. [4:55].

Shipping to the Lab

Before shipping, consult with the testing facility to determine what day samples should and should not be shipped. Many facilities will not have anyone on site to receive packages over the weekend, and you don't want your samples to degrade while sitting in a shipping facility. 
  • Know which days the testing lab receives shipments [5:22].
  • Notify the lab when you have sent a shipment [5:41].

Author: ASM Global Health Programs

ASM Global Health Programs
Read the latest about ASM's Global Health Programs to learn how ASM is helping scientists all over the globe make the world a better place.