A comparative study on the performance of asbestos-free depth-filters for removal of pyrogens from infusion fluids

Our plain-English summary of A comparative study on the performance of asbestos-free depth-filters for removal of pyrogens from infusion fluids, by C. Baggerman, C. Brandsema, M. Humer, et al (The Journal of Pharmacy and Pharmacology, 1981).

The study

• Authors: C. Baggerman, C. Brandsema, M. Humer, J. Visser
• Journal: The Journal of Pharmacy and Pharmacology
• Published: 1981;33(11):685-91
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Three asbestos-free depth-filters were compared with traditionally used asbestos-containing depth-filters for chemical integrity, physical integrity and pyrogen retention. With chemical and physical integrity only minor differences between the various filter types were seen. One asbestos-free depth-filter, based on charcoal, showed poor pyrogen-retention; this might be due to a high flow rate used. Asbestos-free depth-filters based on kieselguhr or on a mixture of kaolin and alumina proved to be good alternatives; these filters have proved to be suitable for the removal of pyrogens from electrolyte- or carbohydrate-containing infusion fluids.

In plain English

This laboratory study, from the Central Laboratory of the Netherlands Red Cross Blood Transfusion Service in Amsterdam, compared an asbestos-containing depth-filter (Seitz EKS) with three asbestos-free depth-filters. The asbestos-free filters were made with kieselguhr, with kaolin and alumina, or with charcoal. The study tested how well each filter removed fever-causing bacterial substances (pyrogens) from infusion fluids. The study did not examine people or health effects. The authors passed water for injection through each filter and measured what the filters released into the filtered fluid. They then filtered test fluids containing added E. coli endotoxin. The asbestos-free filters released significantly more conducting substances than the asbestos filter. The kieselguhr and kaolin filters released more alkaline substances, and the asbestos filter released the most oxidizable matter. Higher particle counts appeared only in early samples. The charcoal filter retained endotoxin poorly from water, at a flow beyond the manufacturer's advised maximum. With Ringer's solution, the asbestos and kieselguhr filters became more efficient as filtration continued. The authors concluded that the kieselguhr and kaolin filters were good alternatives to asbestos for water, electrolyte and carbohydrate solutions.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory comparison of four commercial depth-filters (one asbestos-containing, three asbestos-free) for chemical integrity, physical integrity and pyrogen retention
• Who was studied: No human or animal subjects. Four filters were tested: asbestos (Seitz EKS), kieselguhr (Seitz EKS Supra), kaolin and alumina (Filtrox AF-S-steril) and charcoal (Seitz AKS). The test solutions were water for injection, NaCl 0.9%, dextrose 10% and Ringer's solution. The work was done at the Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, Amsterdam. Dates of the work are not given.
• Exposure: Filtration of infusion fluids through an asbestos-containing depth-filter versus asbestos-free alternatives. For chemical and physical integrity, 90 litres of water for injection were passed through 0.2 m2 of filter at 80 litres per hour. For pyrogen retention, 500 ml of test solution containing 100 ng per ml E. coli endotoxin was passed through a 42 cm2 filter. The asbestos fiber type in the tested filter is not stated. The introduction says chrysotile is the main component of asbestos depth-filters in general.
• Main results:
  • The kieselguhr and kaolin filters released significantly larger amounts of alkaline substances.
  • Release of soluble conducting substances was significantly higher for the asbestos-free filters than for the asbestos filter.
  • The asbestos filters released the most oxidizable substances, and the charcoal filter released none. After 10 litres had been filtered, all filters were within the Ph. Eur. limit for oxidizable matter in water for injection.
  • Significantly larger numbers of particles in the filtrate were seen only in the early (3, 10 and 25 litre) samples.
  • With water as the test solution, the charcoal filter showed poor pyrogen retention, and the authors did not test it further.
  • With Ringer's solution, the asbestos and kieselguhr filters became more efficient as filtration continued. The same was seen for the asbestos filter with NaCl 0.9%. In its worst performance, the kieselguhr filter still reduced the endotoxin content about twenty-fold.
  • With water for injection and a tenfold higher endotoxin load (1000 ng per ml), all samples from the asbestos, kieselguhr and kaolin filters were below the detection level.
• The authors' conclusion: The authors concluded that, for water and for electrolyte- or carbohydrate-containing solutions, asbestos was not superior. In their view, the kieselguhr and kaolin filters were good alternatives, and the kaolin filter even seemed superior to the asbestos filter.
• Limitations the authors state:
  • The sensitivity of the particle-counting method was reduced by high background counts and large variation between individual samples.
  • The flow rate used for the charcoal filter was far above the manufacturer's advised maximum.
  • The authors had no explanation for the increasing filtration efficiency seen during some runs.
  • The filters were not tested with solutions containing amino-acids, plasma substitutes or antibiotics. The authors stated that further research is needed for these.

Related studies

• A routine for the control of the performance of microscopists evaluating airborne asbestos fibre samples on membrane filters by phase contrast microscopy — J.R. Hoyes, R. Clayton (1980)
• Performance of membrane filters used for TEM analysis of asbestos — J.S. Webber, A.G. Czuhanich, et al. (2007)
• Efficiency of sampling and analysis of asbestos fibers on filter media: implications for exposure assessment — D.A. Vallero, J.R. Kominsky, et al. (2009)
• The influence of external aerodymanic factors on the measurement of the airborne concentration of asbestos fibres by the membrane filter method — A.M. Johnston, A.D. Jones, et al. (1982)
• Local inflammatory response produced by solutions sterilized with asbestos type filters — R.S. Speirs, U. Wenck (1955)
• Comparison of a fibrous aerosol monitor (FAM) with the membrane filter method for measuring airborne asbestos concentrations — P.J. Iles, T. Shenton-Taylor (1986)

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