The case for common reference intervals

The current paradigm for pathology reference intervals is for each laboratory to determine its own interval for use with each test offered by the laboratory. It is our contention that this approach does not best serve the medical community, especially at a time when electronic databases of health information are being expanded and integrated. We also believe that this approach is not performed well in many laboratories and is excessively expensive in practice. In contrast, we believe that the preferable option is to develop and apply common reference intervals throughout Australia and New Zealand, together with common reporting formats and assay standardisation wherever this is possible.

We are aware that these are neither trivial nor simple issues, however we believe that failure to achieve this goal where technically possible will be a failure of the pathology profession to meet the challenges of the modern health community.

     

Prerequisites for use of common reference intervals

The theory of reference values was developed more than 30 years ago, but its application in most clinical laboratories is still incomplete today. This is for several reasons, the most relevant ones being the lack of standardisation of the analytical methods, resulting in method-dependent values, and the difficulty in recruiting the proper number of reference subjects for establishment of reference intervals. With the recent progress in method standardisation the first problem is reducing while the second can be addressed optimally via multicentre collaborative studies that aim to establish common reference intervals. To be effective this approach requires the following prerequisites: 1) the existence of a reference measurement system for the analyte; 2) field methods producing results traceable to the reference system; and 3) a carefully planned multicentre reference interval study. Such a procedure will produce results traceable to the reference measurement system for a large number of reference subjects, under controlled pre-analytical conditions. It will also enable a better understanding of the various sources of population variability, if there is the need for partitioning of a reference interval or if there are any limitations to adopting the established reference intervals on a national or global scale. Once reference intervals are determined, clinical laboratories can adopt a common reference interval provided: 1) the population that the laboratory services is similar to the one studied; 2) methods producing traceable results are used; and 3) analytical quality is within defined targets of precision and bias. Moreover, some validation of the interval using a small sample of reference individuals from the laboratory's population is advisable.     

Hematologic and biochemical reference intervals for Spanish ibex

We studied blood samples from 529 Spanish ibexes (Capra pyrenaica) from different Andalusian mountain ranges in southern Spain, primarily from Sierra Nevada. For each sample, 13 hematologic and 32 biochemical parameters were analyzed. Within this database, we selected values obtained from live, free-ranging, physically restrained, clinically normal animals to determine reference intervals for these parameters. Distribution of values within each parameter was determined and differences in values between sex and age classes also were determined. We found significant differences in eight biochemical parameters among male and female ibexes. Significant differences in values for 20 hematologic and biochemical parameters between age classes also were found.     

Pediatric reference intervals for muscle coenzyme Q10

Coenzyme Q₁₀ (CoQ₁₀) is present in humans in both the reduced (ubiquinol, CoQ₁₀H₂) and oxidized (ubiquinone, CoQ₁₀) forms. CoQ₁₀ is an essential cofactor in mitochondrial oxidative phosphorylation, and is necessary for ATP production. Total, reduced and oxidized CoQ₁₀ levels in skeletal muscle of 148 children were determined by HPLC coupled with electrochemical detection, and we established three level thresholds for total CoQ₁₀ in muscle. We defined as “severe deficiency”, CoQ₁₀ levels falling in the range between 0.82 and 4.88 μmol/g tissue; as “intermediate deficiency”, those ranging between 5.40 and 9.80 μmol/g tissue, and as “mild deficiency”, the amount of CoQ₁₀ included between 10.21 and 19.10 μmol/g tissue. Early identification of CoQ₁₀ deficiency has important implications in children, not only for those with primary CoQ₁₀ defect, but also for patients with neurodegenerative disorders, in order to encourage earlier supplementation with this agent also in mild and intermediate deficiency.     

Biochemical and hematologic reference intervals for free-ranging desert bighorn sheep

Over 200 clinically normal desert bighorn sheep (Ovis canadensis) from multiple geographic areas were sampled utilizing a uniform protocol. The goals of this study were to develop comprehensive reference intervals for hematologic and biochemical analytes using central 90th percentile nonparametric analyses. Adult female sheep had greater erythrocyte mass (hemoglobin and hematocrit) compared with adult male sheep. Young animals < or = 1-yr-old had greater erythrocyte mass (hemoglobin, hematocrit and red blood cell count), higher alkaline phosphatase activity, and lower serum protein and globulin concentrations compared with adult animals. Because of the large sample size, wide geographic range, and uniform sample and handling protocol in this study, these reference intervals should be robust and applicable to other free-ranging desert bighorn sheep populations.     

Standardisation of Gymnema sylvestre r. Br. with reference to gymnemagenin by high-performance thin-layer chromatography

A simple and reproducible HPTLC method for the determination of gymnemagenin (1) in Gymnema sylvestre has been developed. Components were separated on pre-coated silica gel 60 F254 plates with chloroform:methanol (9:1) and scanned using a densitometric scanner in the UV reflectance mode at 290 nm. Linearity of determination of 1 was observed in the range 4-10 microg. The average percentage recovery of 1 from an extract was 99.09 +/- 0.29, and the content of 1 in leaves of the title plant was 1.61% (dry weight).     

Mitotic mechanisms: an alternative view

The mechanisms that control spindle structure and move chromosomes remain as mysterious as ever. Using the diatom as a model spindle type, several interesting and counter-intuitive possibilities have emerged. For example, there may not be an anaphase motor and a primary energy-requiring (force-producing) mechanism may actually move chromosomes away from the pole. Force may be a primary factor controlling microtubule assembly disassembly.