Preliminary work on the development of a novel detection method for osteoporosis.

Osteoporosis affects both the organic and mineral phases of bone resulting in a decrease in resistance to fracture. Dual x-ray absorptiometry (DEXA) scans are used for diagnosing osteoporosis, which is conventionally characterised by a decrease in mineral density. Unfortunately, some patients who suffer osteoporotic fractures have normal bone density, because both the organic and the mineral phase are affected. However, there are currently no methods of evaluating the health of the organic phase. Patients undergoing treatment for osteoporosis have reported hardening of their fingernails. As the properties of nail and bone may be linked in a comparable, measurable way, this work used both mechanical (nano-indentation) and chemical (Raman spectroscopy) methods to evaluate differences between fingernails sourced from osteoporotic and non-osteoporotic patients. The difference in mean modulus between the nails sourced from the groups was 1.1 GPa. The disulphide bond content of fingernail samples from each group was measured by Raman spectroscopy and disulphide bond content of fingernail was found to be significantly lower in the osteoporotic group. It can be concluded that a relationship between the mechanical and chemical properties of nail and bone may exist in a measurable way. This work has suggested that changes in the organic phase of bone are reflected in similar proteins, such as keratin, from which fingernails are composed. Collagen and keratin are two distinct structural proteins, but they share the need for protein sulphation and disulphide bond formation, via cysteine, for their structural integrity. A disorder of either process should lead to disordered collagen and keratin synthesis.

The use of fingernails as a means of assessing bone health: a pilot study.

BACKGROUND: Anecdotally, patients volunteer reports of increasing hardness of their fingernails within months of starting diverse treatments for osteoporosis. The properties of both nail and bone may be linked in a comparable, measurable way. METHODS: We examined the fingernails of two groups of patients, with (n = 9) and without (n = 13) osteoporosis at either the hip or lumbosacral spine. We performed nanoindentation to assess the degree of nail brittleness and Raman spectroscopy to assess the disulfide bond content of nail. RESULTS: The mean moduli of fingernails of patients with low bone mineral density (BMD) are lower than those of patients with normal BMD. The mean difference in mean modulus between the groups was found to be 0.996 (p = 0.15 between groups). The spectroscopy data also showed differences between the two sets of nails. The disulfide bond content of the nails sourced from osteoporotic patients was lower than that from healthy patients (p = 0.06 between groups). CONCLUSIONS: Bone collagen and nail keratin are two distinct structural proteins, and both require protein sulfation and disulfide bond formation, via cysteine, for structural integrity. A disorder of either process may lead to disordered collagen and keratin synthesis. This is reflected in the structural abnormalities seen in clinical syndromes in which there is either protein deficiency, disorders of sulfur metabolism, or cystathione beta-synthase deficiency. The relationship between nail and bone may exist in a measurable way. This pilot study should lead to further work to explore this relationship. Could nail prove to be a valuable adjunct to diagnosis or provide a means of more rapid follow-up after commencement of therapy?

The College of American Pathologists, 1946-1996. Quality Assurance Service.

Since its creation in 1970, the College of American Pathologists Quality Assurance Service Committee has provided important and highly respected interlaboratory programs for daily quality control. In 1988, this committee extended its domain by announcing Q-Probes, a unique benchmarking program for laboratory quality assurance. Because of the success and rapid growth of this program during the next 2 years, the Quality Assurance Service Committee expanded into two committees, namely, QAS-QC and QAS-QA, with expertise concentrated, respectively, in quality control and quality assurance. These committees have compiled a history of significant scientific and educational contributions to members, the international laboratory community, other physicians, and patients. New directions for both committees are now underway so that their contributions can continue in the rapidly changing field of pathology and laboratory medicine.

Laboratory precision performance: state of the art versus operating specifications that assure the analytical quality required by clinical laboratory improvement amendments proficiency testing.

OBJECTIVE: To estimate the percent of laboratories with precision performance sufficient to satisfy the operating specifications and guarantee the quality required by the proficiency testing criteria defined by the Clinical Laboratory Improvement Amendments of 1988 (CLIA). DESIGN: Cumulative distributions that describe state-of-the-art laboratory imprecision were obtained for 1500 laboratories participating in the 1990 College of American Pathologists Quality Assurance Service. Allowable imprecision was estimated from the x-intercepts of charts of operating specifications prepared for commonly used single and multirule quality control procedures having two to four control measurements per run. MAIN OUTCOME MEASURE: The derived values for allowable imprecision were imposed on the cumulative distributions to obtain graphical estimates of the percent of laboratories satisfying the operating specifications. RESULTS: Up to 28% of laboratories achieve the imprecision allowable for albumin, up to 64% for total bilirubin, 52% for calcium, 35% for chloride, 48% for cholesterol, 28% for cortisol, 84% for creatinine, 9% for digoxin, 61% for glucose, 64% for high-density lipoprotein cholesterol, 88% for hemoglobin, 95% for potassium, 66% for total protein, 18% for sodium, 29% for thyroxine, 87% for triglycerides, 35% for urea nitrogen, and 81% for uric acid. CONCLUSION: Improvements in precision are still needed for many laboratory tests to assure the analytical quality required by the CLIA proficiency testing total error criteria.

Analytic goals, concentration relationships, and the state of the art for clinical laboratory precision.

We analyzed the College of American Pathologists' Quality Assurance Service 1990 database of 1500 clinical laboratories to evaluate concentration relationships and the state of the art for the precision of 37 analytes. We compared these data to previously reported Quality Assurance Service precision performance data from 1974 through 1980. The general trend of decreasing average long-term, within-method, within-laboratory coefficients of variation continues. However, among 24 routine chemical and therapeutic drug monitoring tests observed for 11 to 16 years, 11 showed no evidence of continuous improvement in precision. The 1990 average coefficients of variation usually exceeded analytic goals modeled by clinical responses when these models assumed that variability in test results arises solely from the analytic performance of the method. In contrast, they usually did not meet goals that take into account the presence of biologic factors among the sources of test variation. Notable exceptions are the average coefficients of variation for cholesterol and triglycerides, which markedly decreased during the National Cholesterol Education Program initiatives of the 1980s. Continuous improvement of precision in disciplines dominated by relatively mature automated methods may not be the norm unless structure and direction are provided by appropriate and accepted analytic goals.

Proficiency test performance and experience with College of American Pathologists' programs.

We examined rates of unacceptable results in a large interlaboratory proficiency test program, which is designed for small hospitals, clinics, and physician offices. The objective was to see whether rates of unacceptable results decrease as laboratories gain experience in interlaboratory comparison programs. We examined data from the College of American Pathologists' Excel Surveys, 1987 through 1993, in the areas of chemistry, hematology, immunology, and blood bank. The data for laboratories with consistent participation show consistent and statistically significant improvement in performance for the first 3 to 4 years of proficiency testing. The data for all participants also suggest that laboratories with more experience with proficiency testing have lower rates of unacceptable results, and that these rates tend to decrease with each year of experience. These conclusions support the findings of other researchers who have documented the benefits of interlaboratory comparison programs and proficiency testing.

The stability of survey-assigned assay values when surveyed control materials are used in a daily interlaboratory quality control program. The College of American Pathologists Chemistry Survey--Quality Assurance Service shared pool experience.

Two pools of lyophilized human control serum, distributed as challenges for the 1990 and 1991 College of American Pathologists Comprehensive Chemistry Surveys were employed consecutively as two-level, daily, quality control materials in College of American Pathologists Quality Assurance Service Regional Quality Control programs. Because the Chemistry Survey and Quality Assurance Service use identical method codes and the materials are essentially stable, the variation of differences among Chemistry Survey and Regional Quality Control assay values is a sensitive measure of both the variation of accuracy among calibrator-assigned values and of the matrix response among calibrator/reagent lots following the time of initial Chemistry Survey assay. In the two cycles of data comparison, the Regional Quality Control means for the assay values of 15 stable routine chemistry analytes showed no statistically significant differences from the initial Chemistry Survey for 295 of 361 analyte-method combinations studied 16 months later. Statistically significant changes between Chemistry Survey assay values and Regional Quality Control means most often occurred with closed rather than with open analytic systems and were predominantly in the same direction at both concentration levels. The magnitude of bias difference was usually less than the average within-laboratory standard deviation for the same analyte concentration. Of 64 analyte-pool combinations studied, a single instance of probable analyte instability was noted, ie, decreasing level I glucose during the first cycle. Our findings strongly support the usefulness of Chemistry Survey-assigned target values to help strengthen the intralaboratory accuracy base. They also point out the need for and the utility of Regional Quality Control-recalculated interlaboratory means to supplement assay values assigned at the time a control pool was put into use.

Quality assurance programs in the United States.

The College of American Pathologists (CAP) provides quality assurance programs for clinical laboratories, including surveys for external quality assessment, quality assurance service for internal and regional quality control, and Q-probes for overall quality assurance including pre- and post-analytic factors. These are complemented by inspections through the laboratory accreditation program and a standards program linked with the national reference system for clinical chemistry. Expert resource committees, organized according to scientific disciplines, provide professional support and direction for these programs. Numerous other professional societies jointly sponsor various surveys, which optimize available expertise, size, and quality of these programs. CAP surveys are the most widely used programs for proficiency testing (PT) in the United States. PT programs only partially characterize performance. Clinical laboratories are best evaluated by a combination of measures, including EQA, internal and regional quality control, monitors of pre- and post-analytic quality, and inspection.

Matrix effects and accuracy assessment. Identifying matrix-sensitive methods from real-time proficiency testing data.

Retrospective proficiency testing data may be used to screen for matrix effect, which is suspected when significant methodologic bias is detected. Prioritization is centered on those situations where relatively high unacceptability rates are associated with high bias. Before attributing high unacceptability rates to methodologic bias, factors such as peer grouping strategies, number of participants in peer groups, analyte concentration, evaluation limits, and interparticipant precision, all of which affect scoring, need to be considered. When bias-associated high unacceptability rates are detected, methods are candidates for further evaluations to identify the causes of bias, to determine if matrix effect is present. Using outputs from the College of American Pathologists Survey Management Enhancement Program, we have presented data from the 1991 Comprehensive Chemistry Survey to demonstrate methodology to study this problem, and have selected examples of method performance in which tabular and graphic information contribute to its study. For the analytes studied, unacceptability rates tend to be greatest in association with high methodologic bias and/or between-participant imprecision relative to external evaluation limits, samples at the upper extreme of analyte concentration, low numbers of participants in peer groups, grading by comparative method, and concentration-independent fixed evaluation limits. Specific examples of significant bias that is possibly matrix induced are presented for uric acid, glucose, creatinine, and total protein.

Multiprogram characterization of laboratory bias, precision, and total error. Proposal for improved assessment with shared external and expanded internal (regional) quality control pools.

We establish that, for the analytes aspartate aminotransferase, glucose, phosphorus, and potassium, there is significant correlation between laboratory performance as determined by College of American Pathologists-sponsored external (Surveys) and expanded internal (regional) quality control (Quality Assurance Service) programs. However, relatively low parametric and nonparametric correlation coefficients and significant departure of linear regression slopes from unity reflect major differences in the calculated parameters of absolute bias, precision, and total error obtained through internal and external quality control. Significantly better performance in both Surveys and the Quality Assurance Service was documented for laboratories participating in the College of American Pathologists Laboratory Accreditation Program. Multiple descriptors of laboratory quality, as indicated here, are superior in describing laboratory performance to proficiency testing alone. As a bridge between external and internal quality control, shared pools of quality control materials are described for use as unknown Survey challenges and subsequent distribution for regional quality control. Such programs, which can be configured to serve thousands of laboratories, could offer cost savings, better quality assurance, and improved characterization of laboratory performance by minimizing interprogram differences in control matrix and method classification and providing greater reliability of target values.

Stability of mean assay values of magnesium and iron in lyophilized quality control serum: a study based on data from the quality assurance service (QAS) of the College of American Pathologists.

Data from magnesium and iron analyses of pools of lyophilized quality control serum were used to evaluate stability of analyte mean values in the pre-reconstitution period. Information was received from laboratories in Regional Quality Control Programs between 1977 and 1981, using CAP Quality Assurance Service data processing. For magnesium, 28 of 41 (68%) pool-method combinations were stable, 11 (27%) showed decreases, and 2 (5%) showed increases. Decreases averaged 0.008 mg/dL/month (all methods). A pronounced effect of method (automated methylthymol blue) and year correlated with decreases in measurable magnesium. For iron, 45 of 56 (80%) pool-method combinations were stable, 8 (15%) showed decreases, and 3 (5%) showed increases. Decreases averaged 0.349 g/dL (all methods). In most cases, changes in measured concentrations are attributed to methodologic factors, rather than intrinsic changes in analyte concentrations.

Glucose stability in lyophilized chemistry quality control serum. A study of data from the quality assurance service (QAS) program of the College of American Pathologists.

Data from 2.5 million glucose analyses on pools of lyophilized human quality control serum were used to evaluate analyte stability in the prereconstitution phase. Input information was from laboratories in Regional Quality Control Programs that use CAP Quality Assurance Service (QAS) data processing. Of 31 pools in use between 1977 and 1981, decreasing glucose concentration was detected by, at least, one method in 26 pools, and by two or more methods in 21 pools. Method-associated average decrease in concentration varied from 0.13 mg/dL/month (glucose oxidase-electrode) to 0.19 mg/dL/month (automated glucose oxidase-colorimetric). Bidirectional instability as a function of analytic method, i.e., increase with "mild" methods, decrease with "rigorous" methods that was noticed previously with pools analyzed between 1973 and 1977, was no longer seen. Dominant directional changes in the later pools were downward by all methods, when statistically significant trends were demonstrated.

Analytic clinical laboratory precision. State of the art for selected enzymes.

Results of precision estimates are reported for selected enzyme analytes. Laboratories that participated in regional quality control programs supplied data to a centralized data processing service (College of American Pathologists Computer Center). These data, representing several regional groups which used different commercial sources of control serum, were statistically analyzed by regression of coefficient of variation (CV) upon concentration of analyte using a modified polynomial regression technic. Tolerance limits for long-term within-laboratory precision were developed from this data. Estimated CVs were extracted at selected analyte concentrations, and tolerance limits for CVs at these concentrations were developed. In addition, selected individual methods within the larger groups were individually examined to evaluate effect of control material matrix upon clinical estimates of enzyme precision. Differences in selected method groups are discussed.

Analyte stability in clinical chemistry quality control materials.

Maximum stability of analytes in chemistry control materials is desired. Stability testing is customarily performed by manufacturers, both prior to distribution of products and during the period following distribution when the products are in the field. Users and evaluators of such materials periodically have reported on experienced stability of various analytes in distributed manufactured products. A wide variety of both testing protocols and definitions of acceptable stability have characterized published reports on the topic. In the present review, we summarize published studies on control material stability in clinical chemistry, review criteria employed to define instability, and present an approach to evaluating stability of analytes involving both statistical and clinical criteria.

Stability of sodium and potassium in lyophilized quality control serum. A study of data from the Quality Assurance Service Program of the College of American Pathologists.

The long-term prereconstitution stability of sodium and potassium in large pools of lyophilized quality control serum used in Regional Quality Control Programs, conducted between 1977 and 1980 is reviewed. In approximately one third of 27 pools studied, minimal but significant increases in sodium concentration were detected, these increases averaged less than 0.50 per year and confirmed our previously reported results from pools analyzed between 1973 and 1976. Results relating to potassium stability have been inconsistent. The previously reported tendency for potassium to increase in some pools was again suggested by data obtained from laboratories using automated flame-emission photometry procedures. This was not confirmed, however, by the data reflecting manual/semi-automated flame-emission photometry procedures or automated electrode methods. It is postulated, that the source of sodium causing the increases in concentration is the glass containers in which control materials are stored between the time of manufacture and reconstitution. Regression analysis against time of monthly interlaboratory means, from participants in Regional Quality Control Programs, is a useful tool for evaluating postmanufacture stability of analytes in pools used for daily internal quality control procedures.