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system. The setup is similar to their previous microinterIn that respect, it has potential for use as a flow sensor for ferometric backscatter detector (Anal. Chem. 1999, 71, on-chip, picoliter volume, time-resolved enthalpy measure369 A), but instead of whole capillaries, the new detector ments, he says. has etched channels, which have the shape of a half capilThe sensitivity of the detector has already been improved lary or hemisphere, on fused-silica or by switching from a slit/photodiode glass chips. to an avalanche photodiode detector “We didn’t think that if we were to (APD), says Bornhop. “When we cut a capillary in half, put a plate on went to an APD, we got a better sigtop of it, and shine a light on it, we nal output for the same photon flux,” would get good interference pathe explains. They also found that terns,” says Bornhop. But they did. changing from a He–Ne to a diode “Not only do we get high-contrast laser source reduced the noise in the fringes, but the fringes shift spatially system. A correction feedback loop in a way that is very sensitive to the that keeps the intensity of diode lasers optical pathlength changes of the stable is responsible for this drop in fluid in the channel.” In other words, noise, says Bornhop. He–Ne lasers if the detector is configured properly, don’t have such a correction and it can sense RI changes. therefore often have large intensity In its current configuration, the fluctuations. on-chip RI detector can measure mi“Ultimately, the way to do this exBackscatter interference pattern produced cromolar levels of solutes in picoliter periment is with a position sensor,” from the interaction of an unconditioned volumes, but efforts to improve its says Bornhop. “Because what you relaser beam with an etched channel. Shifts in sensitivity are under way. “To really ally want to do is measure the position fringe patterns indicate changes in the reapply it to the kinds of things we’d of the fringe as a function of time and fractive index of the solution. like to, we are probably a factor of 5 not necessarily its intensity.” Those away,” says Bornhop. He envisions experiments are currently under way. the detector being used for applicaUsing an optical model, they are tions such as quantitative protein sequencing and with CE also examining what effect the ratio of the cover slide to for high-throughput screening. “You could multiplex the substrate thickness has on fringe spacing and shift. “The device and have multiple separations analyzed simultaneous- hangup right now is trying to get the chips made in the ly,” he adds. In addition to RI changes, the on-chip detec- appropriate dimensions, to confirm that the predicted imtor is capable of sensing millidegree temperature changes. provement is what we get empirically.” Britt Erickson
GOVERNMENT AND SOCIETY Clinical diagnostics in need of standards In vitro diagnostic (IVD) medical devices in the European Union (EU) market were allowed to begin displaying a stamp of approval or CE mark on June 7, which indicates compliance with European Directive 98/79/EC. The first use of this new label marks a major milestone in a 5-year transition period, which began with the publication of the directive in December 1998. Worldwide, the IVD market is estimated at $20 billion (excluding home test kits), with about $5.6 billion of that coming from Europe. Although
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laboratory supplies, such as reagents and calibrators, make up the majority of the IVD market, analytical instruments comprise about 13% of it. IVD products are used in many applications, from diagnosing diseases to determining the effectiveness of medical treatments to identifying microorganisms in food and drugs. The directive is intended to eliminate trade barriers within Europe and ensure better measurements for health care decision making by creating a single mark of approval for all IVD products on the EU market. Over 60% of the EU’s IVD market, however, is imported from the United States, which,
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as many U.S. IVD manufacturers fear, currently does not have the necessary resources to meet the requirements of the directive. By December 2003, all new IVD products on the EU market must have the CE mark. Existing IVD products without the CE mark can only remain on the market until December 2005. If U.S. manufacturers are unable to get the CE mark on their IVD products in time, they will lose the ability to sell their products in Europe. According to Willie May, chief of the Analytical Chemistry Division at the U.S. National Institute of Standards and Technology (NIST), one of
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the major requirements of the directive is that products be traceable to “standards of the highest order,” such as internationally recognized certified reference materials (CRMs). Currently, however, there are no CRMs or reference methods for several hundred analytes that are measured in clinical laboratories. As a result, European laboratories commonly use clinical reference laboratories “to establish traceability to higher-order methods.” Such reference laboratories, however, typically do not exist in the United States, making it difficult for U.S. manufacturers to establish traceability. Traditionally, NIST has developed and maintained standard reference
methods and materials for >25 health status markers, including calcium, chloride, cholesterol, creatinine, glucose, lithium, magnesium, potassium, sodium, trigylcerides, urea, and uric acid. Now, with the added impetus of a potential trade barrier for U.S. IVD manufacturers, NIST plans to significantly expand that list. “Our long-term target is to maintain responsibility for about 40% of the well-defined analytes [that are measured in medical laboratories],” says May. Many of the new markers under consideration are proteins, peptides, and other large biomolecules, which are typically present at low concentrations in biological matrixes. For ex-
ample, NIST has begun developing reference systems for measuring the heart-specific protein troponin-I, which is used to determine whether a person has had a heart attack and the severity of the attack, and glycated hemoglobin, which is used in the diagnosis and monitoring of diabetes. Markers for anemia (iron deficiency), hemochromatosis (too much iron), nutritional health status, prostate and breast cancer, thyroid function, and neural tube defects are also high on the list of those needing reference systems. NIST will hold a workshop in November to address measurement traceability in IVD testing. Britt Erickson
NELAC accreditation delayed
in the first round have certifications that will expire be-
In an emergency meeting in May, the board of directors of
tween now and January 2001. It is undecided whether
the National Environmental
these laboratories will need to
Laboratory Accreditation
renew their certifications or
Conference (NELAC) voted to
whether their existing certifica-
delay the announcement of
tions will be extended until
the first class of NELAC ac-
January, when they can be re-
credited laboratories, which was scheduled for this month,
placed by NELAC certification. The NELAC board of direc-
until January 2001.
tors is currently working with the states to resolve this
The decision was made because of concerns regarding insufficient time for laboratories to comply with the NELAC
issue so that laboratories don’t end up paying double accreditation fees.
proficiency testing requirements. “Although we are disap-
NELAC is a nationwide effort to reduce the number of
pointed in the postponement, we believe that it is more im-
accreditations required for U.S. environmental laboratories
portant to assure the integrity of the program than to meet
to conduct business in more than one state (Anal. Chem.
the July 2000 goal,” wrote NELAC Chair Jim Pearson in a
1999, 71, 329 A–331 A). Despite yet another setback, NELAC
memo notifying accrediting authorities of the decision.
officials are optimistic that implementation of the program
Some laboratories that expect to be NELAC-accredited
will continue to move forward. Britt Erickson
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