Testing Hygrometers Used in Cytogenetics Laboratories for Metaphase Preparation

Thomas Hartley1, Karen Dun2

1 Pathology Services, Royal Hobart Hospital, Hobart, Tasmania, Australia, 2 Cytogenetics Laboratory, Pathology Services, Royal Hobart Hospital, Hobart, Tasmania, Australia
Publication Name:  Current Protocols in Human Genetics
Unit Number:  Appendix 2F
DOI:  10.1002/0471142905.hga02fs70
Online Posting Date:  July, 2011
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Abstract

This protocol describes procedures for checking small laboratory hygrometers for accuracy at three relative humidity (rh) levels. The work arose out of the need to provide laboratory assessors with documentary evidence that the hygrometer used to monitor humidity in the vicinity of the laboratory where medical cytogenetics testing slides are prepared and dried in the ambient environment is reproducible and sufficiently accurate. The procedure is based upon the physicochemical principle that when water or certain saturated salt solutions are placed into a sealed environment, the humidity will equilibrate to well defined levels. We choose to check our hygrometers at three points: 95%, 75%, and 33% rh, using distilled water, saturated sodium chloride solution, and saturated magnesium chloride solution, respectively. Our results have demonstrated that the procedure is convenient and of sufficient accuracy to be fit for this annual hygrometer validation purpose. The procedure takes 24 hr per relative humidity point checked. Curr. Protoc. Hum. Genet. 70:A.2F.1‐A.2F.8 © 2011 by John Wiley & Sons, Inc.

Keywords: Hygrometer check; ISO 15189; slide drying; environmental humidity; chromosome spreading; chromosome crossovers

     
 
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Table of Contents

  • Commentary
  • Literature Cited
  • Figures
  • Tables
     
 
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Materials

Basic Protocol 1:

  Materials
  • Sodium chloride (BDH, Analar grade)
  • Magnesium chloride (anhydrous; Merck, Product Code 8.14730.0100)
  • Polyethylene bucket and air‐tight lid (165 mm diameter × 1400 mm deep)
  • Clear overhead projector film
  • Double‐sided adhesive tape
  • 100‐ml beakers
  • Pieces of expanded polystyrene
  • Test hygrometer: for this protocol the authors used a Testo 608‐H1 hygrometer, humidity/dew point/temperature instrument (Testo, Unit 11,114‐118; http://www.testo.com)
  • Computer running Excel for Windows 2003 for data manipulation and curve fitting
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Figures

Videos

Literature Cited

Literature Cited
   Ahlada Rao, M.R., Victor, R., Rao, P.A., Vasudev, P., Kumari, P., and Rao, V.A. 2005. Slide making and prototype of a dropper device for chromosomal preparations. Int. J. Hum. Genet. 5:213‐216.
   Barch, M.J., Knutsen, T., and Spurbeck, J. (eds.) 1997. The AGT Cytogenetics Manual, Chapter 2. Lippincott‐Raven, Philadelphia.
   Greenspan, L. 1977. Humidity fixed points of binary saturated aqueous solutions. J. Res. Natl. Bur. Stand. A Phys. Chem. 81A(1):89‐96.
   Spurbeck, J.L., Zinmeister, A.R., Meyer, K.J., and Jabel, S.M. 1996. Dynamics of chromosome spreading. Am. J. Hum. Genet. 61:387‐393.
   Standards Australia. 2001. AS4633‐2004 (ISO 15189:2003). Medical Laboratories—Particular Requirements for Quality and Competence. Standards Australia International Ltd., Sydney, Australia.
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