|Year : 2013 | Volume
| Issue : 1 | Page : 28-31
Pattern of serum total alkaline phosphatase activity in different stages of normal third trimester pregnancy in Zaria, Northern Nigeria
Ibrahim S Aliyu1, Abdullahi J Randawa2, Hassan S Isah1, Olumuyiwa A Afonja3
1 Department of Chemical Pathology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
2 Department of Obstetrics and Gyneacology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
3 Department of Clinical Pathology, Lagos University Teaching Hospital, Lagos, Nigeria
|Date of Web Publication||18-Oct-2013|
Ibrahim S Aliyu
Department of Chemical Pathology, Ahmadu Bello University Teaching Hospital, Zaria
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: There are reports from many parts of the world on the increased activity of serum total alkaline phosphatase (TALP) in pregnant women, especially during the last half of pregnancy. There is no such documented finding in this environment. There is the need to determine the serum TALP activity in different stages of normal 3 rd trimester pregnancy in Zaria to allow for proper interpretation of this analyte at this stage of pregnancy.
Subjects and Methods: A cross sectional descriptive study carried out among 100 healthy pregnant women in their 3 rd trimester. They were randomly selected from the antenatal clinic of Ahmadu Bello University Teaching Hospital, Zaria. Serum TALP activity was measured using the 4-Nitrophenylphosphate (4-NPP) method. Socio-demographic and obstetrics characteristics were obtained using an administered questionnaire. Microsoft Excel (Microsoft office, 2003) was used for data analysis. Distributions of ALP activities were found to be skewed; hence, non-parametric analyses using percentiles were used in measuring the variation. A P-value of equal to or less than 0.05 (P ≤ 0.05) was considered as statistically significant.
Results: The serum TALP activity in normal 3 rd trimester pregnancy was found to be higher when compared to the normal population, with a gradual increase with advancing gestational age. Subjects in the gestational age group of 28 to 30 weeks had a serum TALP activity of 46-138 IU/L, with a continuous increase of up to 213 IU/L at 39 weeks of gestation. A sudden drop in activity was observed at the gestational age of 40 weeks and above. The overall serum TALP activity in normal 3 rd trimester pregnancy was found to be 41-206 IU/L.
Conclusion: A higher serum TALP activity for normal 3 rd trimester pregnancy was confirmed for this environment, as has been found elsewhere. There is the need to interpret serum TALP activity in pregnancy with caution.
Keywords: Total alkaline phosphatase, third trimester pregnancy, Northern Nigeria
|How to cite this article:|
Aliyu IS, Randawa AJ, Isah HS, Afonja OA. Pattern of serum total alkaline phosphatase activity in different stages of normal third trimester pregnancy in Zaria, Northern Nigeria. Ann Nigerian Med 2013;7:28-31
|How to cite this URL:|
Aliyu IS, Randawa AJ, Isah HS, Afonja OA. Pattern of serum total alkaline phosphatase activity in different stages of normal third trimester pregnancy in Zaria, Northern Nigeria. Ann Nigerian Med [serial online] 2013 [cited 2020 Feb 27];7:28-31. Available from: http://www.anmjournal.com/text.asp?2013/7/1/28/119984
| Introduction|| |
Alkaline phosphatase (ALP) is present in many tissues of the body with particularly high levels in the liver, bone, placenta, intestine and kidney. These are referred to as isoenzymes.  The precise metabolic function of the enzyme is still unknown, but some suggestions made is that it participates in the calcification process in bone synthesis, and is involved in the transfer of glucose and fatty acids across the cell membrane. 
It is one of the most commonly measured enzymes in the investigation of many diseases such as biliary disease, bone disease, and foeto-placental insufficiency.  The tissue-specific characteristics of ALP are retained when the enzymes are released into the circulation and can be used to identify the tissue responsible for the elevation of the serum activity of the enzymes. ,
ALP is elevated in the serum in pregnancy, especially during the second and third trimesters. Serum total alkaline phosphatase (TALP) begins to rise at the fourth (4 th ) month of gestation.  This elevation is a reflection of placental ALP entering the maternal blood, since human trophoblastic cells are rich in ALP. Measurement of serum ALP of placental origin is, therefore, of particular interest in the investigation of placental insufficiency.  Also, extremely high serum TALP concentrations should arouse suspicion of bone, hepatic, endocrine, renal, or malignant diseases.
The increase in the serum total ALP during the 2 nd half of pregnancy was first recognized by Coryn  in 1934, whose observation has since been confirmed by other investigators. ,, The increase becomes apparent during the 2 nd trimester and continues throughout the 3 rd trimester reaching peak at term, The excess usually disappears within a few weeks after delivery. 
The study is, therefore, designed to determine the activity of serum TALP in the different stages of normal 3 rd trimester pregnancy in our environment, Zaria, Northern Nigeria.
| Subjects and Methods|| |
A total of 100 women with normal pregnancy at different stages of the 3 rd trimester gestation attending the antenatal clinic of Ahmadu Bello University Teaching Hospital (ABUTH), Zaria, were randomly selected for the study. Fifteen were at 28-30 weeks of gestation, 17 at 31-32, 40 at 33-36 weeks, 22 at 37-39 weeks, and 6 at 40 weeks and above. In all selected subjects, gestational age was determined from the date of last menstrual period, clinical measurement of the fundal height, and ultrasonographic estimation. All subjects with present or past history of bone, hepatobiliary, kidney, or gastrointestinal diseases were excluded from the study. All pregnant women below the age of 17 years were excluded. Socio-demographic and obstetrics characteristics were obtained using an administered questionnaire.
Approval for the study was obtained from the Ethical and Scientific Committee of Ahmadu Bello University Teaching Hospital, Zaria; and informed consent was obtained from all subjects.
Venous blood specimen was collected from the antecubital vein of each subject. The skin over the site of collection was swabbed with methylated spirit and allowed to dry. A tourniquet was then applied 10 cm above the antecubtal fossa so as to distend the veins with blood. Sterile 21G size hypodermic disposable needles and syringes were used to draw blood. The blood was then transferred into plain specimen bottles containing no anticoagulant. After 30-45 min when the sample would have clotted, serum separation was carried out by centrifugation at 4000 rpm for 10 min.
The activity of serum TALP was then measured. Sample analysis was carried out for every specimen on the same day of collection. The 4-nitrophenylphosphate (4-NNP) method, which is in use in the ABUTH chemical pathology laboratory, was used for the analysis of samples in this study. The ALP hydrolyses 4-NPP at a pH of 10.3 and temperature of 37° C to liberate 4-nitrophenol (yellow complex). The total serum ALP activity was obtained by reading the absorbance of the 4-nitrophenol at 510 nm using the spectrophotometer.
The within-run and between-run precision profiles were assessed using pooled sera and all were within acceptable limit; thus, the method was found to be precise.
Quality control sera provided by BIOTECH Laboratories Ltd, with low, normal, and high levels of ALP activity were analyzed with each batch of assays to ensure their validity.
Distributions of ALP activities were found to be skewed; hence, nonparametric analysis using percentiles were used in measuring the variation.
| Results|| |
The clinical and laboratory characteristics of the subjects are presented in [Table 1]. The age of this group of subjects ranged from 17 to 45 years with a mean age of 26.7 years. The mean gestational age was 34.5 weeks. The subjects had a mean parity of 2.6 and a mean blood pressure (systolic blood pressure/diastolic blood pressure) of 110/70 mm Hg. The mean serum TALP was 125 IU/L.
[Table 2] shows the serum TALP activity in normal pregnant women at different gestational ages. There's a peak activity of TALP at 38 weeks of gestation. The 2.5, 50, and 97.5 percentile of serum TALP activities are shown in [Table 3]. The 2.5 and 97.5 percentiles of TALP activity is found to be 41-206 IU/L and can serve as the reference interval for our normal pregnant population. The 2.5, 50, and 97.5 percentiles of TALP activity in relation to the gestational ages are shown in [Table 4]. These can also serve as reference intervals for each gestational age group of pregnant women in our environment.
|Table 2: Serum total alkaline phosphatase activity in relation to gestational age of the subjects|
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|Table 3: Percentiles of serum total alkaline phosphatase activity of the study group|
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|Table 4: Reference intervals of serum total alkaline phosphatase activity in different gestational ages of the subjects|
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| Discussion|| |
The established normal range of serum TALP activity for nonpregnant adults in this environment using the same method is 21-92 IU/L. In this study, the mean TALP activity in serum of normal pregnant women in their 3 rd trimester was found to be 125 IU/L. The percentiles of the serum TALP activity showed an activity of 41, 124, and 206 IU/L for 2.5, 50, and 97.5 percentiles, respectively. Using the 2.5 and 97.5 percentiles as reference interval, the reference range for serum TALP activity was determined to be 41-206 IU/L in normal 3 rd trimester pregnant women. This study, therefore, confirms an increase in serum TALP activity in normal pregnancy. This finding is similar to those of Meranze, Posen, Beck, Meade, and Okesina. ,,,,
Statistically significant differences in serum TALP activity were also found between the gestational age groups (P < 0.001). The higher the age of pregnancy, the higher is the activity, with a peak at 37-39 weeks of gestation. Towards term, however, the activity slightly decreases. These findings was similarly reported by Okesina et al.,  in Ilorin, Afonja et al.,  and Adeniyi and Olatunbosun  in Lagos.
The serum TALP activity in pregnancy is higher because it is composed of ALP from placenta (heat-stable ALP), and ALP from other sources other than placenta such as liver and bone; with the highest contribution coming from the placenta. , Following the above findings in this study, we were able to establish a higher serum TALP activity (41-206 IU/L) in normal 3 rd trimester pregnancy for this environment, in Northern Nigeria.
| Conclusion|| |
The study has confirmed that the serum TALP activity is higher in normal pregnancy with gradual rise with advancing gestational age. Similarly, reference interval of serum TALP for normal 3 rd trimester gestation in this environment has been established.
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[Table 1], [Table 2], [Table 3], [Table 4]