Feasibility of a rapid method to evaluate platelet survival time

The purpose of this study was to evaluate the feasibility of a shorter method of performing platelet kinetic studies with respect to the conventional 8-9-day approach.

METHODS

We studied 41 patients (28 women, 13 men; mean age 52 yr) with primary idiopathic thombocytopenic purpura (ITP) (n = 20), secondary ITP (n = 9), HCV associated thrombocytopenia (n = 9), splenectomy (n = 1) and hairy-cell leukemia (n = 1). The patients were in a steady-state of platelet turnover. Initial platelet counts ranged from 19 to 302 x 10(9)/liter (mean value = 83). Platelet survival times (PST) were measured from the blood radioactivity disappearance curve of 111In-oxine-labeled autologus platelets following the recommendations of the International Committee for Standardization in Haematology: blood samples were taken at 30 min and 2 and 4 hr and thereafter daily for 7 days. PST was calculated by the weighted mean method and ranged from 18 to 219 hr (mean value = 98). PST was also calculated using only the data collected at 2, 48 and 96 hr. If the radioactivity in the blood at 96 hr exceeded 10% of the 2-hr value, the additional point at 168 hr was used.

RESULTS

By using this reduced dataset, we obtained a correlation of r = 0.97 with the PST obtained from the whole dataset. In 24 patients, the difference was between +/- 10 hr and exceeded 1 day in only 4.

CONCLUSION

About 94% of the data may be recovered with only three or four blood samples and the duration may be shortened to 4 days in a significant proportion of patients (48% of ITP patients). This approach offers the advantages of increased patient throughput, compliance and reduced examination costs.

The clinical value of prostate-specific antigen and bone scintigraphy in the staging of patients with newly diagnosed, pathologically proven prostate cancer

Recent reports suggest that radionuclide bone scan (BS) may not be necessary in the standard staging evaluation of patients with prostate cancer when serum prostate-specific antigen (PSA) levels are normal. To evaluate the ability of PSA to predict BS findings, we retrospectively reviewed the case records of 118 consecutive patients (median age 73 years, range 50-90 years) with newly diagnosed, untreated, pathologically proven prostate cancer who underwent BS and serum PSA sampling within a period of no more than 3 months. Fifty-four out of 118 BSs demonstrated metastatic bone disease. A PSA value of less than 10 ng/ml excluded bone metastasis; of 35 patients with a serum PSA level of 20 ng/ml or less, seven had a positive BS (negative predictive value of 80%). These findings provide additional confirmation of the value of low serum PSA concentrations in excluding the need for a staging BS, although the threshold for a high value of negative predictive accuracy is lower than previously reported.