Alex Prins - Academia.edu (original) (raw)

Papers by Alex Prins

Research paper thumbnail of Stability of ascorbic acid in serum and plasma prior to analysis

Annals of Clinical Biochemistry, 2002

The stability of ascorbic acid in serum and plasma prior to analysis was studied. Blood samples w... more The stability of ascorbic acid in serum and plasma prior to analysis was studied. Blood samples were collected from ten healthy subjects into Vacutainer tubes containing either dipotassium EDTA, lithium-heparin or no additive. Ascorbic acid was analysed following immediate separation and preservation of samples, following delayed separation for 2 h and after delayed deproteinization and preservation for 2, 5 and 8 h. Deproteinization and preservation were achieved using a solution containing perchloric acid, EDTA and dithiothreitol. Ascorbic acid was analysed by high-performance liquid chromatography. Blood collected into EDTA and separated, deproteinized and preserved immediately gave the highest yield of ascorbic acid. Loss of analyte after delayed separation was least for EDTA tubes (median 7%, range 4-13%), followed by lithium-heparin (median 18%, range 10-32%) and serum (median 26%, range 14-50%). Immediate separation of samples but delayed deproteinization and preservation also resulted in substantial losses of ascorbic acid. Minimum loss of ascorbic acid is achieved if blood is collected into tubes containing dipotassium EDTA and separated within 2 h, followed by immediate deproteinization and preservation.

Research paper thumbnail of Iron Supplementation: Oral Tablets Versus Intramuscular Injection

Non-anemic, iron depleted women were randomly assigned to an injection group (IG) or oral group (... more Non-anemic, iron depleted women were randomly assigned to an injection group (IG) or oral group (OG) to assess which method is more efficient for increasing iron stores over a short time period. IG received a course of 5 x 2 mL intramuscular injections over 10 d, and OG received one tablet daily for 30 d. Fourteen, 21 and 28 d after commencing supplementation, ferritin concentration in OG significantly increased from baseline (means +/- standard error: 27 +/- 3 to 40 +/- 5 to 41 +/- 5 to 41 +/- 5 microg/L; P < 0.01). Similarly, on days 15, 20, and 28 post the first injection, ferritin concentration in IG significantly increased from baseline (means +/- standard error: 20 +/- 2 to 71 +/- 17 to 63 +/- 11 to 63 +/- 7 microg/L; P < 0.01), and was also significantly greater than OG at day 15 and 28 (P < 0.05). Iron injections are significantly more effective (both in time and degree of increase) in improving ferritin levels over 30 d than oral tablets.

Research paper thumbnail of Transferrin Index: An Alternative Methodfor Calculatingthe Iron Saturation of Transferrin

We surveyed 140 clinical chemistry laboratories in Australia to establish which laboratory method... more We surveyed 140 clinical chemistry laboratories in Australia to establish which laboratory methods they used to determine serum iron status: 125 measured serum iron (Fe), 85 measured transferrin (TRF), 47 measured total iron-binding capacity (TIBC), and 14 measured both TRF and TIBC. Of the 55 laboratories routinely reporting TRF saturation (TS), 16 calculated IS directly as (FeIflBC) x 100, and 9 used [Fe/(TRF x 2)] x 100. Thirty laboratories measured TRF and converted it to an equivalent TIBC concentration;

Research paper thumbnail of Effect of Iron Injections on Aerobic-Exercise Performance of Iron-Depleted Female Athletes

This investigation examined the effect of intramuscular iron injections on aerobic-exercise perfo... more This investigation examined the effect of intramuscular iron injections on aerobic-exercise performance in iron-deficient women. Sixteen athletes performed a 10-min steady-state submaximal economy test, a VO2max test, and a timed test to exhaustion at VO2max workload. Subjects were randomly assigned to an iron-supplemented group (IG) receiving intramuscular iron injections or to a placebo group (PG). Twenty days after the first injection, exercise and blood testing were repeated. A final blood test occurred on Day 28. Post supplementation, no differences were found between the groups' submaximal or maximal VO2, heart rate, or blood lactate (P > 0.05). Time to exhaustion was increased in the IG (P < 0.05) but was not greater than that of the PG (P > 0.05). The IG's serum ferritin (SF) was significantly increased on Days 20 and 28 (mean +/- standard error: 19 +/- 3 to 65 +/- 11 to 57 +/- 12 microg/L; P < 0.01), with a percentage change from baseline significantly greater than in the PG (P < 0.01). It was concluded that intramuscular iron injections can effectively increase SF without enhancing submaximal or maximal aerobic-exercise performance in iron-depleted female athletes.

Research paper thumbnail of Stability of ascorbic acid in serum and plasma prior to analysis

Annals of Clinical Biochemistry, 2002

The stability of ascorbic acid in serum and plasma prior to analysis was studied. Blood samples w... more The stability of ascorbic acid in serum and plasma prior to analysis was studied. Blood samples were collected from ten healthy subjects into Vacutainer tubes containing either dipotassium EDTA, lithium-heparin or no additive. Ascorbic acid was analysed following immediate separation and preservation of samples, following delayed separation for 2 h and after delayed deproteinization and preservation for 2, 5 and 8 h. Deproteinization and preservation were achieved using a solution containing perchloric acid, EDTA and dithiothreitol. Ascorbic acid was analysed by high-performance liquid chromatography. Blood collected into EDTA and separated, deproteinized and preserved immediately gave the highest yield of ascorbic acid. Loss of analyte after delayed separation was least for EDTA tubes (median 7%, range 4-13%), followed by lithium-heparin (median 18%, range 10-32%) and serum (median 26%, range 14-50%). Immediate separation of samples but delayed deproteinization and preservation also resulted in substantial losses of ascorbic acid. Minimum loss of ascorbic acid is achieved if blood is collected into tubes containing dipotassium EDTA and separated within 2 h, followed by immediate deproteinization and preservation.

Research paper thumbnail of Iron Supplementation: Oral Tablets Versus Intramuscular Injection

Non-anemic, iron depleted women were randomly assigned to an injection group (IG) or oral group (... more Non-anemic, iron depleted women were randomly assigned to an injection group (IG) or oral group (OG) to assess which method is more efficient for increasing iron stores over a short time period. IG received a course of 5 x 2 mL intramuscular injections over 10 d, and OG received one tablet daily for 30 d. Fourteen, 21 and 28 d after commencing supplementation, ferritin concentration in OG significantly increased from baseline (means +/- standard error: 27 +/- 3 to 40 +/- 5 to 41 +/- 5 to 41 +/- 5 microg/L; P < 0.01). Similarly, on days 15, 20, and 28 post the first injection, ferritin concentration in IG significantly increased from baseline (means +/- standard error: 20 +/- 2 to 71 +/- 17 to 63 +/- 11 to 63 +/- 7 microg/L; P < 0.01), and was also significantly greater than OG at day 15 and 28 (P < 0.05). Iron injections are significantly more effective (both in time and degree of increase) in improving ferritin levels over 30 d than oral tablets.

Research paper thumbnail of Transferrin Index: An Alternative Methodfor Calculatingthe Iron Saturation of Transferrin

We surveyed 140 clinical chemistry laboratories in Australia to establish which laboratory method... more We surveyed 140 clinical chemistry laboratories in Australia to establish which laboratory methods they used to determine serum iron status: 125 measured serum iron (Fe), 85 measured transferrin (TRF), 47 measured total iron-binding capacity (TIBC), and 14 measured both TRF and TIBC. Of the 55 laboratories routinely reporting TRF saturation (TS), 16 calculated IS directly as (FeIflBC) x 100, and 9 used [Fe/(TRF x 2)] x 100. Thirty laboratories measured TRF and converted it to an equivalent TIBC concentration;

Research paper thumbnail of Effect of Iron Injections on Aerobic-Exercise Performance of Iron-Depleted Female Athletes

This investigation examined the effect of intramuscular iron injections on aerobic-exercise perfo... more This investigation examined the effect of intramuscular iron injections on aerobic-exercise performance in iron-deficient women. Sixteen athletes performed a 10-min steady-state submaximal economy test, a VO2max test, and a timed test to exhaustion at VO2max workload. Subjects were randomly assigned to an iron-supplemented group (IG) receiving intramuscular iron injections or to a placebo group (PG). Twenty days after the first injection, exercise and blood testing were repeated. A final blood test occurred on Day 28. Post supplementation, no differences were found between the groups' submaximal or maximal VO2, heart rate, or blood lactate (P > 0.05). Time to exhaustion was increased in the IG (P < 0.05) but was not greater than that of the PG (P > 0.05). The IG's serum ferritin (SF) was significantly increased on Days 20 and 28 (mean +/- standard error: 19 +/- 3 to 65 +/- 11 to 57 +/- 12 microg/L; P < 0.01), with a percentage change from baseline significantly greater than in the PG (P < 0.01). It was concluded that intramuscular iron injections can effectively increase SF without enhancing submaximal or maximal aerobic-exercise performance in iron-depleted female athletes.