Search PubMed⌕ Search

Biomedical subjects

R Hellman

Publications and source records attributed to R Hellman.

7 recordsLinked to original sources
PubMed1992

A multisite physician's office laboratory evaluation of an immunological method for the measurement of HbA1c.

OBJECTIVE: To evaluate the clinical performance of a new immunological HbA1c method in physicians' office laboratories. RESEARCH DESIGN AND METHODS: Three physicians' offices participated in the evaluations. The clinicians routinely use HbA1c test results to monitor their patients' long-term blood glucose control. Precision and interlaboratory variability were assessed using three levels of lyophilized controls. Correlation of the method's results to currently available laboratory methods was made. Comparison of finger-stick (capillary) results to venous EDTA whole blood results was made on 134 patients. Physician and laboratory personnel input was evaluated with regard to the clinical utility of the system. RESULTS: The CVW and CVB were a maximum of 4.5 and 4.4% for the immunoassay system on three levels of control materials at the three sites. Interlaboratory variability among the control means was found to be 4.9-5.4, 8.0-8.3, and 11.7-12.0% HbA1c. Correlation coefficients (r) ranged from 0.95 to 0.99. There was a positive bias by the DCA 2000 compared with the in-house method at site 1. Minimal negative biases were seen by the DCA 2000 with comparative methods used at sites 2 and 3. Median percentage differences with the comparative methods were 12, -1.4, and -5.6%. Comparison of capillary to venous sample results, from the DCA 2000, showed no clinically significant differences. Operator and physician feedback were positive with respect to technical ease in performance of the test and accuracy of results. CONCLUSIONS: Precision was acceptable and interlaboratory variability was low. The immunological method correlated well with manual ion-exchange and automated HPLC methods. The small sample size and good comparison between capillary and venous sample results make fingerstick sampling acceptable. The method provided immediate test results (within 9 min) to the clinicians.

Blood Specimen Collection↗
PubMed1987

Why can a decrease in dB(A) produce an increase in loudness?

Loudness measured by the method of absolute magnitude estimation is compared to loudness calculated in accordance with ISO 532 B (International Organization for Standardization, Geneva, 1966). The measured and calculated loudness functions exhibit a similar pattern of loudness growth. Both measured and calculated loudness of a complex sound composed of a 1000-Hz tone and broadband noise is a nonmonotonic function of the overall SPL of the complex. The nonmonotonic loudness-growth pattern holds over a 30-dB range from 73.5 to 103.5. To facilitate understanding of the results, a single cycle of data is analyzed in detail. The analysis shows that loudness patterns produced in the auditory system by the tone-noise complex can account for the observed effects. Moreover, they show that the A-weighting and the loudness of the complex are negatively related. This inverse relation means that the A-weighted SPL is an inappropriate and misleading indicator of the loudness of sound combinations with heterogeneous spectral envelopes. Consequently, its suitability for noise control is diminished. A loudness meter that combines the spectral shapes of different sounds to produce an overall perceived magnitude offers greater promise.

Acoustic Stimulation↗
PubMed1987

On the relation between the growth of loudness and the discrimination of intensity for pure tones.

The intensity jnd is often assumed to depend on the slope of the loudness function. One way to test this assumption is to measure the jnd for a sound that falls on distinctly different loudness functions. Two such functions were generated by presenting a 1000-Hz tone in narrow-band noise (925-1080 Hz) set at 70 dB SPL and in wideband noise (75-9600 Hz) set at 80 dB SPL. Over a range from near threshold to about 75 dB SPL, the loudness function for the tone is much steeper in the narrow-band noise than in the wideband noise. At 72 dB SPL, where the two loudness curves cross, the tone's jnd was measured in each noise by a block up-down two-interval forced-choice procedure. Despite the differences in slope (and in sensation level), the jnd (delta I/I) is nearly the same in the two noises, 0.22 in narrow-band noise and 0.20 in wideband noise. The mean value of 0.21 is close to the value of 0.25 interpolated from Jesteadt et al. [J. Acoust. Soc. Am. 61, 169-176 (1977)] for a 1000-Hz tone that had the same loudness in quiet as did our 72-dB tone in noise, but lay on a loudness function with a much lower slope. These and other data demonstrate that intensity discrimination for pure tones is unrelated to the slope of the loudness function.

Acoustic Stimulation↗
PubMed1987

Pseudohyperphosphatemia and dysproteinemia.

We report the case of a patient with IgG multiple myeloma and pseudohyperphosphatemia, and the case of another patient in whom unexplained hyperphosphatemia led to the diagnosis of monoclonal gammopathy. The pseudohyperphosphatemia was due to the interference of monoclonal immunoglobulins with the phosphomolybdate colorimetric assay for phosphorus determination widely in use with some automated systems. Ultrafiltration of these patients' serum samples resulted in normalization of the elevated phosphorus values. Knowledge of this phenomenon may obviate confusion, unnecessary testing, and expenditure. It may also provide clinicians with a clue as to the presence of a dysproteinemia.

Aged↗
PubMed1985

The Coulter Counter leukocyte differential.

The leukocyte differential counting capability of the Coulter Counter model S-PLUS IV was evaluated for precision, accuracy, and clinical sensitivity. The evaluation used procedures described in the NCCLS tentative standard (H20-T) when these were appropriate for this technology. Within its inherent constraints, the system was found to be more reproducible than the stained-film reference method and at least as accurate. Clinical sensitivity was equivalent to that of a four-slide, microscope differential count. Reference ranges for the cell classes identified by the instrument were similar to those given by the stained-film method.

Biometry↗