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Biomedical subjects

A Loría

Publications and source records attributed to A Loría.

At least 19 recordsLinked to original sources
PubMed1979

Serum ferritin in an elderly population.

Serum ferritin was assayed by an immunoradiometric method in 82 people above 60 years of age. For comparison purposes, the same assay was performed in 71 younger normal adults. The serum ferritin distribution in the elderly had a larger variance than in the younger adults and in addition, there was a clear shift to higher values in the elderly. The latter was more notable in females than in males but there was still a statistically lower mean in elderly females than in elderly males. Ten out of 55 elderly subjects with evidence of iron deficiency (response to oral iron therapy) had a normal or high serum ferritin which suggests that variables unrelated to iron status may operate in determining serum ferritin levels in the elderly. The shift to higher values appears to occur upon reaching grossly 70 years of age. Whether the shift is a physiologically normal event is at present an open question.

Aged↗
PubMedDate not supplied

[Evaluation of pipetting systems. II. Precision and accuracy of precision dispensers].

OBJECTIVE: To evaluate the precision and accuracy of the liquid dispensers being used in our institution. MATERIAL: A total of 15 dispensers (8 micro and 7 macro) of automatic, semiautomatic or manual types were evaluated. They had been in use from 0.5 to 7 years. METHODS: The volume dispensed was established by gravimetry using an analytical balance (Chio JP-160) and deionized distilled water as previously described. The microdispensers were evaluated using volumes of 20 and 100 microL, and the macrodispensers with 1 and 5 mL. Each dispenser was evaluated using 10 replicates: the mean and the CV (coefficient of variation) were calculated with the 10 replicates. The mean was transformed to per cent of the theoretical volume. Thus a 100% ratio of accuracy corresponds to a perfect accuracy. An important methodological aspect was that the 10 dispensing replicates were performed personally by the habitual user of the dispenser. RESULTS: The mean and CV are shown in table 2 for the microdispensers, and in table 3 for the macrodispenser. In the total 25 evaluation in tables 2 and 3 there were 8 instances in which precision was poor (CV above 3%) and also 8 cases of sizable inaccuracy (ratio outside of 100 +/- 5%). In 4 (2 micro and 2 macro) of these 8 inaccuracies, the error ranged from 10% to 22%. A minority was within the specifications of precision and accuracy claimed by the manufacturers of the dispensers with the exception of the manual microdispensers which were within specifications in most instances. We attribute the latter to the lack of a mechanical device in the manual dispensers. CONCLUSIONS: As in a previous evaluation of automatic micropipettes, we detected a high proportion of pipetting systems out of specifications in both precision and accuracy. The magnitude of error in the accuracy of 4 dispensers (10 to 22%) would be catastrophic in methods demanding good pipetting.

Calibration↗
PubMedDate not supplied

[Patient data for evaluating reference values].

OBJECTIVE: To explore the use of data in patients as a way to evaluate the values of reference in clinical assays. Serum calcium (Ca) and phosphorus (P) were selected for this purpose. MATERIAL: A total of 836 consecutive admissions in a 10 week period were revised. Seventy percent (580 cases) had data of Ca and P in the first week following admission. A total of 424 were excluded by anyone of the following criteria: a) serum urea greater than 50 mg/dL, b) serum creatinine greater than 1.5 mg/dL; c) serum albumin less than 4 g/dL; d) lack of data of either urea, creatinine or albumin. These cutoff values were selected on the basis of a significant difference (t test) in the mean of Ca and/or P in patients grouped according to levels of the available data. The remainder of 156 cases is the selected population of study, and the 580 with Ca and P is the total population. METHODS: Ca and P were assayed in an analyzer (Coulter Chemistry) using the DAM and the Jaffé methods respectively. The precision during the period of study was adequate (CVs of 2.6% for Ca and 2.9% for P). RESULTS: Table 1 compares the mean, SD and CV of Ca and P in the selected versus the total population. There are significant reductions (F test) in the variability of Ca and P in the selected population (from a CV 9 to 5% in Ca and from 35 to 13% in P). Table 2 compares the age and sex distributions of the selected versus the total population. There are no significant differences (chi square test) although there is a lower proportion of people above 80 years of age in the selected population. The reference intervals of Ca and P in the selected population were obtained with the mean +/- 2 SD as both showed Gaussian distributions. These limits are compared in table 3 versus the values of the institution and of the manufacturer of the analyzer used. The P limits of this study fall intermediate to the other two, but in Ca they are the lowest of the three. Shortly after the completion of this study, the institutional values of Ca were changed to 8.5-10.5 mg/dL on the basis of the one year results in a WHO quality assessment scheme. The modification made the Ca limits of this study also intermediate to the other two series. The small differences in the limits have clinical and economic repercussions. Table 4 shows there is a 20% reduction in the number of abnormal tests (206 vs 259) and in the number of abnormal individuals (165 vs 203) using the limits of this study versus the institutional limits before modification. CONCLUSIONS: The data of Ca and P in a selected but representative population of patients proved to be a reliable way of evaluating its reference intervals. The reference intervals of this study were intermediate to those of the manufacturers of the analyzer and the laboratory (after modification). This finding suggests the strategy may be as good as more conventional approaches to establish reference values.

Adolescent↗