Presencia de macroprolactina en sueros con normo e hiperprolactinemia: comparación de dos métodos de detección / Comparison of two techniques to detect the presence of macroprolactin in serum

Background: Macroprolactin is biologically inactive but may be detected by immnoassays. This leads to errors in diagnosis and inadequate treatment of patients with hyperprolactinemia. Aim:To assess two techniques to detect the presence of macroprolactin. Material and Methods: Prolactin was measured by immunoassay in 57 serum samples (from 4 males and 53 females aged33 +/- 13 years), before and after precipitation with polyethyleneglycol (PEG) and separation by ultrafiltration. A significant level of macroprolactin was considered to be present when prolactin detected in the supernatant after PEG precipitation or in the ultrafiltrate was less than 40 percent of the initial concentration of prolactin. Results: Prolactin levels fluctuated from 5 to 411 ng/ml. The percentages of recuperation were independent of the initial prolactin concentration. In 12 and 14 percent of samples, using polyethyleneglycol and ultrafiltration respectively, there was a prolactin recuperation of less than 40 percent. Eight and 11 percent of samples with a prolactin concentration of more than 30 ng/ml, had a recuperation of less than 40 percent using polyethyleneglycol and ultrafiltration respectively. Conclusions: Approximately 10 percent of samples with a prolactin concentration over 30ng/ml have recuperation values suggestive of the presence of macroprolactin. There is a good concordance between precipitation using polyethyleneglycol or ultrafiltration.

Hemofilia A: análisis de intron 18 e intron 7 del gen del factor VIII y su rol en una estrategia de diagnóstico de portadoras en una población chilena / Hemophilia A: analysis of intron 18 and intron 7 of factor VIII gene and its role in a strategy of carrier diagnosis in a chilean population

Hemophilia A is an X-linked disorder of coagulation caused by a deficiency of factor VIII. A large number of different mutations in the VIII gene have been identified. Thus, the detection of female carriers, depends upon the analysis of DNA polymorphism in and near the factor VIII gene. Our aim was to develop a strategy, earlier reported, for carrier testing in families at risk of hemophilia A. In this study, we analyzed the DNA polymorphisms in 26 affected families, with use of the factor VIII intragenic polymorphisms identified by the restriction enzymes Bcll and AlwNI and by differential hybridization with sequence-specific oligonuclaotide probes recognizing Bcll and AlwNI polymorphisms. While the DNA polymorphism detected by Bcll site in intron 18 of the factor VIII gene was informative for 30 percent families studied, the AlwNI/intron 7 polymorphism provided aditional information (4 percent). The carrier status of the remaining 58 percent could be determined utilizing the other polymorphisms suggested the strategy. The 2 polymorphic sites used combined with the other polymorphisms, intragenic and extragenic, can generate levels of informativeness greater than 98 percent. We concluded that the strategy for carrier testing would be a good alternative in genetic counselling for hemophilia A., but its limitations must be carefully taken into account

Resistencia a la proteína C activada: estudio de laboratorio y prevalencia del defecto en la población chilena / Activated protein C resistance: laboratory study and prevalence of the defect in chilean population

Activated protein C resistance (APCR) or factor V leiden has been recently described as the most prevalent hemostatic abnormality associated with venous thrombosis. In patients with familial thrombophilia, the prevalence of APCR is 19-60 percent and around 20 percent in sporadic venous thrombosis. APCR is usually measured by the degree of prolongation of activated Partial Thromboplastin Time (APTT) on patient's plasma, induced by addition of APC in comparison to normal plasma. At the molecular level the defect is caused by a single-point mutation in the gene for factor V (FV) (G1.691-A), that predict the replacement of Arg506 by Glutamine. This mutation makes activated factor V resistant to inactivation by APC. Since the prevalence of the defect is highly variable among different populations, the objective of this work was to study its frequency in our population and in patients with thrombophilia. We defined the normal range for APTT ratio (APTT+APC/APTT-APC) in a group of 73 healthy volunteers in whom the presence of FV Q506 mutation was searched using Mnll enzyme digestion of PCR amplified genomic fragment containing the nucleotide 1.691. The lower limit of APTT ratio stablished in this group was 2.13. APCR was found in 6 out of 159 control subjects (3.8 percent) and in 14/50 (28 percent) of patients with thrombosis. In 13 cases as a single defect and in 1 associated to type I protein C deficiency. All the APCR patients and control subjects were heterozygotes by gene analysis. The results demonstrate that in our population APCR is also the most common defect associated with thrombosis, in accordance with a high prevalence in the population. The ability to screen for this defect will permit the identification of carriers that would benefit preventive therapy at risk situations