December 2007: Volume 33, Number 12
The Growth of Mass Spectrometry Analysis
New Guidance Addresses Lack of Lab Resources
By Melissa D’Archangelo
Mass spectrometry (MS) has been widely used in science and industry for decades, but its considerable analytical advantages have only become available to clinical laboratories in recent years. The technology is now taking on an increasingly important role for analysis of biological samples due to the development of more user-friendly, affordable, and versatile instruments, as well as greater availability of internal standards. Known for its ability to produce high-quality results with superior selectivity, MS is particularly useful for analyzing multiple analytes, such as in expanded newborn screening programs.
Although mass spectrometers have decreased in price and complexity, clinical laboratories interested in employing this technology still must overcome some significant challenges. Developing assays, acquiring high-quality standard materials, training and maintaining highly qualified staff, adopting methods for quality control, and reporting results remain difficult for many laboratories.
“Many clinical chemists are intimidated by a mass spectrometer because it is not a tool that most are trained on or historically have even had an opportunity to use,” said Donald H. Chace, PhD, of Pediatrix Analytical in Bridgeville, Pa., who is chairholder of the Clinical and Laboratory Standards Institute (CLSI) (Wayne, Pa.) subcommittee that developed a recently released guideline for the use of MS in the clinical laboratory. The support networks are not nearly as large as those for commercial auto-analyzers in hospitals, and mass spectrometrists skilled in its operation are often difficult to find.”
Alan L. Rockwood, PhD, of the University of Utah Department of Pathology and ARUP Laboratories in Salt Lake City, Utah, and a member of the CLSI committee, notes that more clinical labs are adopting the technology, but that until now, few applicable resources have been available to them. “Mass spectrometry is in an exponential growth phase, but it is necessary to support that growth with reliable, useful resources to enable the clinical laboratory to address the challenges of using this complex instrument,” he advised. The recently released guideline from CLSI, Mass Spectrometry in the Clinical Laboratory: General Principles and Guidance; Approved Guideline (C50-A), offers a general understanding of MS and the principles that dictate its application in the clinical laboratory (See Sidebar, below).
How to Obtain the Mass Spec Guidance Document
CLSI welcomes comments and questions about its guidance documents. This feedback serves as the basis for updating published documents. All comments and responses are formally addressed and published in the next edition of the document. Mass Spectrometry in the Clinical Laboratory: General Principles and Guidance; Approved Guideline, Document C50-A.
Mass Spectrometry: Then and Now
Because of the cost of equipment, and complexity of sample preparation and interpretation of results, laboratories using MS were often specialized reference or university-based medical centers. However, MS has been a mainstay of metabolic profiling. “The roots of MS in clinical applications are in metabolic profiles, more specifically organic acid analysis in urine extracts,” explained Chace. “A compound could be identified by its retention time and mass-to-charge value. Due to this power and the advent of improved chromatography such as capillary gas chromatography (GC), urine organic acid analysis by GC/MS became the gold standard. Other assays were developed on this platform, such as steroids, amino acids, and carbohydrates, but generally only in highly specialized metabolic laboratories or centers of excellence.”
The development of more user-friendly, affordable, and versatile mass spectrometers has since allowed a large increase in the use of MS for clinical applications. In addition, over the last two decades, advances in ion source design have made it possible to analyze more water-soluble, polar compounds, including peptides, proteins, oligonucleotides, DNA, and trace elements.
One advance that greatly enhanced the application of MS in clinical labs is a process called ionization. “New ionization techniques that allow analysis of polar compounds without the need for extensive derivatization enabled applications in clinical analysis in the late 1980s and early 1990s. For example, some of the metabolites of special interest were organic acids in blood that mark metabolic disease. But, the real developments at this time were not so much in the area of mass analysis, but in ionization—the process of making ions from molecules in solution.”
Thanks to those developments, newborn screening by MS became feasible and continues to be an area where MS is used extensively. “Expanded newborn screening measures many analytes simultaneously from two or more classes of molecules, such as amino acids and fatty acid conjugates known as fatty acylcarnitines,” noted Rockwood. “A mass spectrometer, in particular a tandem mass spectrometer, has good specificity and the ability to measure many analytes simultaneously using a relatively small sample and relatively simple sample preparation.” Mass spectrometers also have high throughputs, Rockwood pointed out. “These qualities combine to make expanded newborn screening practical, whereas it may not be practical when using most other technologies, such as immunoassays.”
Challenges of Using MS
Despite the growth of testing by MS and its many advantages, there remain several challenges to its use in the clinical laboratory. “Few graduates enter the workforce with practical, hands-on experience with mass spectrometers, and without a good understanding of this technology it is possible to generate meaningless or misleading results,” noted Mark W. Duncan, PhD, of University of Colorado Heath Science Center Fitzsimons (Aurora, Colo.), and a member of the CLSI committee.
Although the basic MS technology has been around for decades, a mystique still surrounds its use. “MS has been a rather specialized field, and it is a technology that is somewhat unfamiliar to most people working in clinical laboratories,” Rockwood observed. Along with training and understanding of the equipment, there are other problems with the widespread adoption of MS. “Acquiring high-quality standard materials, such as calibrators and controls, is sometimes a challenge. Maintaining and operating instrumentation to a high standard can also be difficult because mass spectrometers are complex instruments that have not yet been optimized for use in clinical laboratories.” And, as Rockwood points out, “Proficiency testing is still being developed for some analytes for which an MS peer group has not yet been established,”
A Reference and Resource
To help laboratorians offer MS-based testing, the new CLSI MS guideline provides accurate and state-of-the-art information. It is divided into six areas: advantages and disadvantages of the methodology; precautions for the use of MS; quality control considerations; assay verification/validation; approaches to reporting results; and communication of the data. To illustrate these concepts, the document uses concrete examples of how MS is currently being used.
Members of the committee are enthusiastic about what the new guideline offers to both novice and expert laboratorians. “The guideline has been carefully crafted using CLSI’s consensus process with input from a group with diverse experience,” noted Duncan. “If you have little or no experience with mass spectrometry, this is a good place to start.For the expert, the document highlights the areas of importance and draws the critical information together in a single document.”
Rockwood echoes that enthusiasm. “In many cases, the CLSI MS guideline will be where a laboratorian will find answers to questions such as how to set up a selection matrix for matching application classes to instrument types, or what factors to consider when setting up quality control programs.
Committee members also believe that the new document will provide a reference for a large audience serving as an educational resource for both the practitioners of MS and the medical professionals who use the results produced by the instruments for the diagnosis, characterization, or monitoring of disease. In particular, the committee aimed to help medical professionals better understand why MS may be preferred for a clinical application, and allow them to be more informed consumers when selecting a diagnostic laboratory to provide MS services, noted Chace. “A physician may refer to the CLSI MS guideline to determine what advantage a mass spectrometer offers in the analysis of testosterone. A physician may ask, ‘Are MS results more reliable, or simply better for my patients because of a more accurate diagnosis?’ The guideline would be a place to find the answer,” he noted.
The use of MS in clinical labs will no doubt continue to expand, with many exciting possibilities on the horizon. “Soon, nearly every infant in the United States will be screened using tandem MS,” predicted Chace. “Numerous other countries around the world are also embracing this technology. Applications in other areas, including steroid analysis, demonstrate how a mass spectrometer can be used to improve both precision and accuracy when quantifying structurally similar compounds that are present at widely different concentrations. This is an area where immunoassays are often prone to failure or are notoriously unreliable,” he said.
“Although newborn screening is a major clinical application, it primarily resides in specialized laboratories, including public health laboratories. As the larger commercial and private laboratories recognize the advantages of MS, its application will expand to other areas where it can serve to complement other analytical approaches,” he added.
The field of proteomics will also bring more MS applications to labs. As scientists conduct studies aimed at identifying protein biomarkers, MS will be at the heart of most of these biomarker discovery studies. “So far in the clinical laboratory, MS has mainly been applied to the quantitative analysis of small molecules. In the future, we are likely to see this expand into other areas, such as protein and peptide analysis, genetic analysis, and infectious disease testing,” added Rockwood.
Duncan emphasizes the analytical capabilities of MS as the reason that the technology will expand. “The mass spectrometer offers exceptional selectivity as a chromatographic detector. This leads to an increase in both precision and accuracy. Decreasing system costs and complexity now make these benefits accessible in many more situations,” he said. “We will increasingly see mass spectrometers take the place of other systems in the routine testing laboratory.”
Melissa J. D’Archangelo is a marketing and communications consultant based in Chester Springs, Pa.