Biomedical subjects

R O Davis

Publications and source records attributed to R O Davis.

93 records · Page 6Linked to original sources

PubMedDate not supplied

Automated sperm morphometry analysis (ASMA) in the rabbit.

New methods of specimen preparation were developed and a new method of objective, automated sperm morphometry analysis (ASMA) was performed to reduce the technical variation in the rabbit sperm morphology assay. The optimal staining procedure was a modified GZIN stain, which allowed the ASMA instrument to accurately recognize the distal end of the sperm head and to achieve the highest sperm recognition rate (94%). Washing and resuspending sperm to a standard concentration increased the number of sperm per microscopic field in low-concentration samples and reduced the field-to-field variation in all samples. Washing also decreased the number of sperm recognition errors by the ASMA instrument. Mean metric measurements for all sperm were: length, 7.38 microns; width, 3.91 microns; width/length, 0.53; area, 22.10 microns; and perimeter, 19.20 microns. Within-specimen coefficients of variation (CVs) ranged from 0.8% to 5.5% and between-animal CVs ranged from 2.7% to 7.5%. The use of standard specimen preparation techniques and ASMA technology can significantly reduce the technical variation in the rabbit sperm morphology assay.

Animals↗

PubMedDate not supplied

Consistency of sperm morphology classification methods.

The World Health Organization (WHO) recently suggested new morphometric dimensions for normal sperm heads and new sperm head classification rules. These specifications differ from previous WHO methods and from the Kruger method for strict morphology assessment. We analyzed the WHO and Kruger sperm classification rules to determine their appropriateness as predictive linear models. We reviewed the theoretical requirements for allometric modeling, a more traditional approach for specifying the size relationships between phenotypic characters, and developed valid allometric models based on the statistical properties of over 3,700 measurements of individual sperm head dimensions. We implemented the WHO, Kruger, and Allometric methods on the same set of digitized sperm heads to study the empirical consequences of different metric requirements and classification methods. Results show that the WHO and Kruger methods are internally consistent, but specify nonconstant variance. Hence, they are inappropriate linear models. The allometric models were internally consistent and specified constant variance. Hence, they are appropriate linear models. Significant differences were found in the percentage of normal sperm between the methods. On average, the Kruger method produced the lowest value and the Allometric methods produced significantly higher values than the WHO methods, but no average difference was found between WHO methods or between Allometric methods. Nevertheless, the percentage of normal sperm did change significantly for individual specimens. These results indicate that small differences in metric requirements and classification rules can dramatically change the percentage of normal sperm. Until more rigorous definitions of sperm features can be developed, and valid statistical models can be used to describe the population characteristics of fertile sperm, the prognostic value of sperm morphology is limited.

Classification↗

PubMedDate not supplied

Operational standards for CASA instruments.

Computer-aided sperm analysis (CASA) technology is 7 years old. Over 120 papers have been written that verify the technology or apply it in basic and clinical studies. Most of the technical problems with CASA, such as the dependence of velocity on video frame rate, inaccuracy of count and percent motility for low- and high-concentration specimens, parameter dependence on the number of frames analyzed, sensitivity of the subjective threshold setting, confusion over the presence of debris, and different implementations of algorithms across instruments, still persist. A critical review of the literature reveals that no standard practices are followed within or across instruments. Moreover, no standards have been embraced or recommended by professional societies. Despite its potential to provide objective measurements of specimen and individual sperm parameters, and to automate the laboratory semen analysis, the promise of CASA has not been fulfilled. Unless laboratory medicine defines instrument performance and laboratory standards and co-operates with industry to achieve these goals, CASA technology may remain a research curiosity. This outcome is especially worrisome in the context of increasing requirements for laboratory accuracy, precision, standardization, and accreditation under the Clinical Laboratory Improvement Act of 1988.

Diagnosis, Computer-Assisted↗