Maternal serum creatine kinase as a biochemical marker of tubal pregnancy

Role of creatine phosphokinase as a diagnostic marker in tubal ectopic pregnancy

Background and Aim

Ectopic pregnancy (EP) is still one of the leading preventable causes of maternal morbidity and mortality in the first trimester. Amidst the use of sensitive assays for β-HCG and high-definition ultrasonography for the identification of EP, the search for a more reliable and sensitive marker remains a challenge till date. Our aim was to determine the validity of creatine phosphokinase (CPK) and its isoenzyme (CPK-MB) in the prediction of tubal EP.

Materials and Methods

A prospective and comparative diagnostic accuracy study was conducted among 105 pregnant women in the first trimester who met the eligibility criteria in the Department of Obstetrics and Gynecology, North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences (NEIGRIHMS). The study included 35 patients each with tubal EP (EP), abortive intrauterine pregnancy (AP), and normal intrauterine pregnancy (NP). CPK, CPK-MB, and β-HCG were measured among all the participants, and the participants were followed up longitudinally.

Results

A total of 105 pregnant women were included. The mean CPK and CPK-MB levels were significantly higher among the women with EP when compared to NP (P < 0.05) and AP (P < 0.05) women; however, there was no significant difference between the NP and AP groups (P > 0.05). Moreover, the receiver operating characteristic (ROC) curve showed that both CPK and CPK-MB were good predictors of EP, with CPK (area under the curve [AUC] = 0.764) being a better predictor than CPK-MB (AUC: 0.650) in the diagnosis of EP.

Conclusion

Early diagnosis of EP allows appropriate and timely management, which would not only reduce mortality and morbidity associated with the condition but also enable preservation of fertility and improve future pregnancy outcome. Hence, the need of the hour is a reliable biochemical diagnostic marker for EP, such as CPK.

Developing a deeper insight into reproductive biomarkers

The development of biomarkers of reproductive medicine is still in its infancy because many black boxes are still present in reproductive medicine. Novel approaches to human infertility diagnostics and treatment must be developed because reproductive medicine has lagged behind in the implementation of biomarkers in clinical medicine. Despite the dearth of the available literature, the current rapid pace of publications suggests that this gap will soon be filled therefore; this review is a précis of the research that has been done so far and will provide a basis for the development of biomarkers in reproductive medicine.

Ectopic pregnancy: a review

PURPOSE

Ectopic pregnancy (EP) presents a major health problem for women of child-bearing age. EP refers to the pregnancy occurring outside the uterine cavity that constitutes 1.2-1.4 % of all reported pregnancies. All identified risk factors are maternal: pelvic inflammatory disease, Chlamydia trachomatis infection, smoking, tubal surgery, induced conception cycle, and endometriosis. These developments have provided the atmosphere for trials using methotrexate as a non-surgical treatment for EP. The diagnosis measure of EP is serum human chorionic gonadotropin, urinary hCGRP/i-hCG, progesterone measurement, transvaginal ultrasound scan, computed tomography, vascular endothelial growth factor, CK, disintegrin and metalloprotease-12 and hysterosalpingography. The treatment option of EP involves surgical treatment by laparotomy or laparoscopy, medical treatment is usually systemic or through local route, or by expectant treatment.

RESULTS

It was concluded that review data reflect a decrease in surgical treatment and not an actual decline in EP occurrence so that further new avenues are needed to explore early detection of the EP.

Serum biomarkers of tubal ectopic pregnancy: current candidates and future possibilities

Ectopic pregnancy remains a considerable cause of maternal morbidity and mortality worldwide. Currently, it is diagnosed using a combination of transvaginal ultrasound and serial serum beta-human chorionic gonadotrophin levels. Diagnosis is often delayed and these tests are time-consuming and costly, both psychologically to the patient and financially to health services. The development of a biomarker that can differentiate a tubal ectopic from an intrauterine implantation is therefore important. In the pre-genomic era, a one-by-one scientific approach has revealed over 20 candidate biomarkers that could be used as a test to diagnose ectopic pregnancy although at present their clinical utility is very limited. These biomarkers cluster into themes: markers of abnormal embryo/trophoblast growth, markers of abnormal corpus luteum function, markers of a growing pregnancy in the Fallopian tube, markers of inflammation and peritoneal irritation, and uterine markers of normal implantation. It is likely that this thematic approach will facilitate the identification of newer biomarkers using microarray technology and inform the development of investigative paradigms using multiple markers at the time of presentation.

Serum markers in the diagnosis of tubal pregnancy

The introduction of highly sensitive methods, such as transvaginal sonography and measurement of serum b-human chorionic gonadotropin, has dramatically improved ectopic pregnancy diagnosis in recent years. Early diagnosis is the key to successful and conservative management of women with ectopic pregnancy; however, approximately 50 percent of such women are initially misdiagnosed, resulting in significant morbidity and mortality. In order to improve diagnosis, several serum markers are being investigated including progesterone, CA 125, pregnancy-associated plasma protein-A, vascular endothelial growth factor, and maternal creatine kinase. Measurement of serum vascular endothelial growth factor, alone or together with other markers, could be a promising method for earlier and more accurate differential diagnosis. However, the clinical applicability of these findings remains to be evaluated in larger prospective studies.

Do levels of serum cancer antigen 125 and creatine kinase predict the outcome in pregnancies of unknown location?

BACKGROUND

The aim of this study was to evaluate the role of maternal serum cancer antigen 125 (CA 125) and creatine kinase (CK) levels in predicting the outcome of pregnancies of unknown location (PUL).

METHODS

Prospective observational study. Women classified as PUL were recruited. Final outcome of each PUL was established: failing PUL, intrauterine pregnancy (IUP), ectopic pregnancy (EP) or persisting PUL. The persisting PUL group almost certainly represent ultrasonically missed EP and were included in EP group. Serum CK and CA 125 were measured at 0 and 48 h. The values at presentation and the change in levels after 2 days were used in the analysis. We incorporated the most significant of variables into a multinomial logistic regression model to predict all outcomes. The performance of this model was evaluated using receiver operating characteristic (ROC) curves.

RESULTS

In all, 4698 consecutive women were scanned; 403 were classified as PUL, 27 were lost to follow-up. Of the 376 women eligible, 297 had complete data and therefore were recruited. Mean age and mean gestation were 30.0 years and 43.3 days respectively. Final outcomes: 153 failing PUL (51.5%), 116 IUP (39.1%) and 28 EP (9.4%). Mean serum CK levels at 0 and 48 h were 88.5 and 86.8 IU/l respectively. Mean serum CA 125 levels at 0 and 48 h were 43.8 and 40.1 kIU/l respectively. 81.1% of women had CK and CA 125 ratios (CK 48 h/CK 0 h, CA 125 48 h/CA125 0 h) between 0.7 and 1.3. CA 125 ratio was the only significant variable in the three outcome groups (P < 0.0001). Logistic regression analysis incorporating CA 125 ratio gave an area under ROC curve of 0.782 (SE = 0.041) for failing PUL, 0.768 (SE = 0.043) for IUP and 0.560 (SE = 0.078) for EP. This model was capable of distinguishing failing PUL from IUP, but was not able to detect EP.

CONCLUSIONS

Absolute levels of serum CK and CA 125 at the defined times cannot be used to predict the outcome of PUL. Although the CA 125 ratio when incorporated into logistic regression model can distinguish failing PUL from IUP, its inability to detect the high risk PUL, i.e. the developing EP, renders it inappropriate for use in the clinical setting.

Serum levels of myoglobin, creatine phosphokinase, and smooth muscle heavy-chain myosin in patients with ectopic pregnancy

STUDY OBJECTIVE

Serum markers of smooth muscle destruction have been shown to be elevated in ectopic pregnancy, but they remain of questionable clinical utility. Our goal was to determine the clinical utility of 3 markers of smooth muscle destruction: creatine phosphokinase (CPK), smooth muscle heavy-chain myosin (SMHC), and myoglobin.

METHODS

This was a prospective cohort study, with consecutive enrollment of all women in the first trimester of pregnancy who presented to our urban emergency department with complaints of lower abdominal pain, vaginal bleeding, or both. Patients were excluded from the study if there was a history of recent surgery or major trauma. Data analysis included receiver operating characteristic (ROC) curve, 95% confidence intervals (CIs), and a regression model.

RESULTS

A total of 378 patients were enrolled, with 61 patients diagnosed with an ectopic pregnancy, and 317 patients placed in the non-ectopic pregnancy group with other diagnoses. ROC curve analysis revealed an area under the curve of 0.56 (95% CI 0.51 to 0.61) for CPK, 0.63 (95% CI 0.59 to 0.68) for SMHC, and 0.58 (95% CI 0.53 to 0.63) for myoglobin. A regression model analyzing the effects of race, maternal age, estimated gestational age, and serum levels of human chorionic gonadotropin beta-subunit found no significant confounders.

CONCLUSION

Although there is a statistically significant elevation in the serum levels of SMHC, the range of values seen is too large to allow SMHC to be a useful screening tool.

Evaluation of serum creatine kinase as a diagnostic marker for tubal pregnancy

Forty women comprising of 20 each in study and control groups had their serum creatine kinase (CK) estimated. The study subjects were proven cases of ectopic pregnancy and the controls were either medical termination of pregnancy seekers or antenatal cases matched for gestational age and with a confirmed intrauterine pregnancy. Total serum creatine kinase levels were found to be significantly higher in the study group i.e. 34.15 +/- 1.17 IU/L compared to the controls 18.72 +/- 1.25 (p < 0.001). Creatine kinase is estimated routinely in cardiac patients even on an emergency basis. Our findings indicate that when in doubt the test could be used as a marker for the diagnosis of ectopic pregnancy.

Serum progesterone and endovaginal sonography by emergency physicians in the evaluation of ectopic pregnancy

OBJECTIVE

To determine a discriminatory level for serum progesterone (SP) in pregnant patients with no definite intrauterine pregnancy (IUP) on endovaginal ultrasonography (US) in the differentiation of ectopic pregnancy from normal IUPs.

METHODS

A prospective observational study in a convenience sample of women at risk for ectopic pregnancy was performed at an urban teaching hospital from May 1991 until May 1994. Women aged > or =18 years presenting to the ED with a positive pregnancy test in combination with pelvic or abdominal pain, vaginal bleeding, orthostasis, adnexal mass or tenderness, or any historical risk factor for ectopic pregnancy were eligible. Hypotensive or unstable patients were excluded. Endovaginal US was performed and patients with no definite IUP had a serum beta-hCG and SP measured.

RESULTS

314 patients were enrolled, with 14 excluded for lack of follow-up or incomplete SP data, yielding 300 patients. The initial endovaginal US diagnoses included 169 definite IUP, 31 abnormal IUP, 5 definite ectopic pregnancy, and 95 no definite IUP. 68/95 had SP measured, with values of 22.8 +/- 13.4 ng/mL (mean +/- SD) for IUP; 4.9 +/- 6.5 for spontaneous abortion, and 7.5 +/- 7.2 for ectopic pregnancy. The mean values were significantly different (2-tailed t-test) for ectopic pregnancy vs IUP and for spontaneous abortion vs IUP. An SP of > or =11 ng/mL (sensitivity 91%; specificity 84%) was post hoc the best cutoff value for suggesting an IUP when the endovaginal US was not definite for IUP.

CONCLUSIONS

SP cannot reliably discriminate ectopic pregnancy vs spontaneous abortion in pregnant patients with no definite IUP on endovaginal US; however, a low SP (<11 ng/mL) in this sonographic category suggests an abnormal pregnancy.

Serum creatine kinase is an unreliable predictor of ectopic pregnancy

OBJECTIVE

To compare serum creatine kinase (CK) values in patients with ectopic pregnancy vs patients with threatened miscarriage or normal pregnancy.

METHODS

An observational case-control study was performed at an urban teaching hospital. Pregnant women with a quantitative beta-hCG obtained for suspicion of ectopic pregnancy were evaluated. Excluded were cases with recent trauma, i.m. injections, surgery, or history of heart, liver, or muscle disease. The serum beta-hCG and CK values were recorded and compared between groups with 1-way ANOVA and Tukey's multiple comparison procedure at the overall 0.05 level.

RESULTS

The 15 ectopic, 28 threatened miscarriage, and 21 normal pregnancy cases were of similar gestational ages (p = 0.2), ranging from 3 to 12 weeks. Although the CK values for ectopic pregnancy (88.8 +/- 33.6 IU/L) exceeded those for threatened miscarriage (65.9 +/- 59.0 IU/L) and normal pregnancy (56.0 +/- 38.1 U/L) (p = 0.02), there was significant overlap between groups. CK values were at or above a cutoff of 74 IU/L in 80% (95% confidence interval: 52-96%) of ectopic pregnancies, 25% (11-45%) of threatened miscarriages, and 14% (3-36%) of normal pregnancies.

CONCLUSIONS

Although the ectopic pregnancy population is characterized by a higher mean CK than are patients with threatened miscarriage or a normal pregnancy, a significant overlap in CK values makes use of this serum marker unreliable for detecting ectopic pregnancy.