Fetal Fibronectin as a Predictor of Successful Induction of Mid-trimester Abortion: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Fetal Fibronectin as a Predictor of Successful Induction of Mid-trimester Abortion (NCT02694198), a registered phase not stated study. The primary outcome is Cervicovaginal Fetal Fibronectin Level.

2. Clinical Question

3. Trial Design

This is a completed study sponsored by Ain Shams Maternity Hospital. The registry record lists enrollment of 135 and gives a start date of 2015-09 and a primary completion date of 2016-03. It describes fetal fibronectin measurement as the intervention, classified as an other intervention. The listed condition is medical abortion of a fetus.

The record does not describe a randomized allocation, and allocation is not stated. No like-for-like control comparison is identified. The intervention listing indicates that measurement was part of the study, but does not establish that participants were assigned to different strategies or that a treatment effect was being evaluated. The record also does not describe a prospective cohort structure, a diagnostic-accuracy design, or another specific observational design, so those labels should not be inferred.

The primary outcome is a continuous measure: mean cervicovaginal fetal fibronectin level, with standard deviation as the named dispersion measure and a 72 hours timeframe. The registry lists 2 outcome measures, but the available outcome information does not describe the second measure. The record contains no analysis entries and does not report outcome results. It also does not report the recruitment setting beyond the named sponsor, participant flow, exclusions, or whether enrollment and analysis populations were identical.

The population description includes a sample-size rationale referring to an earlier report and a proposed minimum sample size. That description should not be treated as proof of the final analytic sample or as evidence that a particular analysis was conducted. Details of the study protocol, including how induction success was defined and when fetal fibronectin was measured relative to the induction process, are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Depending on Francesco et al., 2005 who found that Fetal fibronectin test positive in 19 among 270 (7.0%) women undergoing mid-trimester abortion. Assuming α=0.05 and confidence interval (CI)= 10.0% and by using PASS 11th release the minimal sample size is 120. With a possible 10% drop out of cases, the enrolled cases would be 135 cases.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Depending on Francesco et al., 2005 who found that Fetal fibronectin positive test in 19 among 270 (7.0%) in women undergoing mid-trimester abortion. Assuming α=0.05 and confidence interval (CI)= 10.0% and by using PASS 11th release the minimal sample size is 120. With a possible 10.0% drop out of cases, the enrolled cases would be 135 cases.

6. Primary Endpoint

The registry lists the primary outcome as Cervicovaginal Fetal Fibronectin Level, measured over 72 hours.

The primary endpoint is the mean cervicovaginal fetal fibronectin level among women undergoing mid-trimester induction of abortion. The unit is nanogram per milliliter, the measure of central tendency is the mean, the named measure of dispersion is standard deviation, and the timeframe is 72 hours. These details describe the intended measurement, but the record does not state more precisely how the timeframe was operationalized.

A mean summarizes the central level across participants, while a standard deviation describes how dispersed individual measurements are around that mean. Together, these statistics can characterize the observed distribution of a continuous biomarker. They do not, by themselves, establish whether the biomarker distinguishes participants who experience one outcome from those who experience another.

The title presents fetal fibronectin as a predictor of successful induction. To evaluate prediction, the outcome being predicted and the way prediction is assessed need to be specified. The registry record does not define successful induction, identify a comparison between success and failure, or report measures of predictive performance. It also does not provide the mean or standard deviation for the primary endpoint. The intended endpoint is therefore identifiable, but its observed value and its relationship to induction success are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous, so its stated summary is a mean with standard deviation. In general, the mean gives a measure of the center of a set of measurements. The standard deviation describes how spread out individual observations are around that center. A mean and standard deviation can be useful for describing a biomarker, but they do not reveal the full shape of its distribution. For example, an unusually skewed distribution or influential extreme measurements can make the mean less representative of a typical observation. The registry does not report the outcome values or distributional details needed to assess those possibilities.

What would a confidence interval communicate?

In general, a confidence interval expresses uncertainty around an estimate using a method with a stated coverage interpretation. A narrow interval indicates greater precision under the assumptions of the method; a wide interval indicates less precision. It is not a guarantee that the true value lies within a particular calculated interval. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed from the posted results.

How would a prediction analysis differ from a mean description?

In general, describing an average biomarker level and assessing prediction answer different questions. A mean describes the observed levels in a group. A prediction analysis must connect the biomarker to a defined outcome, such as a clearly specified induction result, and evaluate how well measurements distinguish or estimate that outcome. Depending on the question, an analysis might examine discrimination, calibration, or performance at a specified decision threshold. Each measure has a distinct interpretation and requires clearly defined outcome and test classifications. The registry record does not report the success definition, a fetal fibronectin threshold, or any such predictive-performance analysis.

Prediction estimates also need precision assessment and a clear account of how the prediction rule was developed and evaluated. General statistical practice distinguishes performance measured in the same data used to develop a rule from performance assessed in separate data or through an appropriate validation method. The registry record does not report a prediction rule or validation approach. No conclusion about predictive accuracy can be made without these details and the associated results.

Why does the comparison structure matter?

In general, a comparison is interpretable only when the groups and the process that formed them are understood. Random allocation, when used, can help balance groups in expectation, while observational comparisons may be affected by differences in participant characteristics or care. Here, allocation is not stated, and no comparator is specified. The record therefore does not support treating any implied arms as randomized or as a direct control comparison. It also gives no adjusted analysis from which to assess how measured characteristics may have been handled.

The record states standard deviation for the primary endpoint, but no model or distributional assumption is reported. General methods for continuous data may rely on assumptions about the outcome distribution or sampling behavior. If measurements are strongly skewed or contain extreme values, alternative summaries or models may sometimes be considered. No distribution checks, transformations, or alternative analyses are described in the registry record, so it is not possible to determine what methods were used.

The sample-size description refers to an earlier estimate of fetal fibronectin test positivity, a stated alpha of 0.05, a confidence interval of 10.0%, use of PASS 11th release, a minimum sample size of 120, and a possible 10% dropout. These are planning details in the population description. They do not establish the analysis performed, the final number with evaluable outcomes, or the precision achieved for the continuous primary endpoint. The record does not report a trial-specific statistical analysis plan or an explanation of how the planning assumptions were translated into the final outcome analysis.

A separate sample-size illustration based on an observed effect, if considered, is a planning exercise rather than observed power. In general, such calculations show how a hypothetical future study might be sized under specified assumptions; they do not describe the probability that this completed study detected an effect. The registry record does not report inferential results for the primary endpoint, so there is no sponsor analysis to compare with a recalculation.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Mid-trimester Abortion")
n   <- c(135)
m   <- c(39.4)
sp  <- c(7.9)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Mid-trimester Abortion  135  39.400  7.900  38.055  40.745

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures, while the available record information describes only the primary outcome. The definition and results for the other outcome are not reported in the registry record. The record contains no analysis entries, and it does not report whether multiple hypotheses, endpoints, subgroups, or time points were tested.

In general, multiplicity arises when several statistical questions are examined. Testing many questions can increase the chance of obtaining at least one apparently noteworthy result by chance, unless the analysis plan addresses that issue. No multiplicity strategy or prespecified hierarchy is reported in the registry record. It is therefore not possible to determine whether multiplicity was relevant to the analyses actually conducted or how it may have been handled.

Missing-data procedures and analysis populations are also not reported in the registry record. The sample-size description mentions a possible 10% dropout as part of planning, but that does not show how many participants had missing measurements, why data may have been missing, or how any missing values were handled. The record does not state whether the primary outcome was analyzed in all enrolled participants or a subset with available measurements. It also does not report imputation, sensitivity analyses, exclusions, or a participant flow account.

These gaps matter because the number and characteristics of participants contributing to an outcome can affect both the estimate and its precision. Without a reported analysis population and missing-data method, the completeness and representativeness of the primary endpoint results cannot be assessed. No assumption about the causes or consequences of missing data should be made from the planning note alone.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry record lists 135 participants at risk for serious adverse events and 0 affected by serious adverse events. It separately lists 135 at risk for other adverse events and 118 affected by other adverse events. No top serious-event terms are listed. Deaths are not reported in the registry record.

These are counts in the registry safety fields, not a full clinical account. The record does not provide descriptions of the other adverse events, their severity, timing, duration, or relationship to the intervention or study procedures. It also does not explain the monitoring period or the criteria used to classify events. The counts should therefore be read as the posted event summary, not as a complete characterization of safety.

A count of 0 serious adverse events means none are recorded in that field; it does not establish that all possible events were captured or that a different study population would have the same experience. Similarly, the other-adverse-event count cannot be interpreted by event type or cause without supporting details. The registry record does not report those details.

13. What the Result Does, and Does Not, Mean

The posted record establishes that a completed study enrolled 135 participants and focused on fetal fibronectin measurement during mid-trimester abortion induction. It specifies a continuous primary outcome: mean cervicovaginal fetal fibronectin level in nanogram per milliliter, with standard deviation and a 72 hours timeframe. Those details identify the study's subject and the measure it intended to summarize.

The record does not report the primary outcome estimate, its standard deviation, or a confidence interval. It also does not define successful induction or report a statistical relationship between fetal fibronectin and that outcome. Thus, the record does not show whether the observed biomarker levels were high or low, how variable they were, or how precisely they were estimated. It cannot establish predictive accuracy or a relationship with induction success.

This absence of reported results should not be mistaken for evidence that the biomarker has no predictive value, nor should the study title be taken as evidence that it does. A title conveys the topic or intended question, while a conclusion requires reported analyses tied to a defined endpoint. Here, the necessary results and endpoint definition are not reported in the registry record.

The listed adverse-event counts offer limited safety information: 0 serious adverse events among 135 at risk and 118 other adverse events among 135 at risk. The nature and context of those events, as well as deaths, are not reported in the registry record. These counts do not resolve the missing efficacy or prediction results.

The most defensible interpretation is therefore descriptive: the registry identifies the planned biomarker measure, the enrollment, and selected record-level details, but does not provide enough outcome information to judge the biomarker's performance or the precision of the primary endpoint estimate.

14. Why This Trial Matters Statistically

This study is statistically interesting because its title poses a prediction question while the recorded primary endpoint is a continuous biomarker mean. That distinction is important: summarizing a marker's average level is not the same as showing that it forecasts a clinical outcome. To make a prediction claim interpretable, the outcome definition, the marker's role, and the evaluation method need to be reported together.

The registry record makes the intended measurement visible, including its unit, summary statistic, dispersion measure, and timeframe. It also identifies enrollment and includes a sample-size rationale. Those details help readers understand what the study set out to measure and what planning considerations were recorded. At the same time, the missing outcome estimates and analysis details illustrate why a registry record's endpoint description should not be treated as a result.

The record also highlights the importance of transparent comparison structure. Allocation is not stated, and no comparator is specified. Without that information, readers cannot decide whether a contrast is causal, descriptive, or based on some other design. Clear reporting of participant flow, analysis populations, missing data, and methods would further help assess whether the reported estimates correspond to the intended population and question.

Finally, the posted safety counts show why counts alone need context. Event definitions, follow-up, and event descriptions are necessary to understand what such numbers represent. In this record, those details are not reported. The statistical value of the entry lies in clarifying what can be identified from the registry and where interpretation must stop because the results and methods are incomplete.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The central limitation is that the registry record does not report the primary endpoint results. The mean cervicovaginal fetal fibronectin level and its standard deviation are not stated, and no interval estimate is reported. As a result, neither the magnitude nor precision of the primary outcome can be evaluated.

The title concerns prediction of successful induction, but the record does not define success or report a prediction analysis. No threshold, comparison of outcome groups, predictive performance measure, or validation procedure is described. This prevents assessment of whether fetal fibronectin was informative for the title's question. The primary endpoint description alone does not answer it.

The comparison structure is also unclear. Allocation is not stated, and no comparator is specified; the record should not be interpreted as a randomized comparison. The registry does not report the second of its 2 outcome measures in the available outcome information, or explain how multiple outcomes or analyses were addressed.

Further details needed to assess generalizability and analysis quality are not reported in the registry record. These include eligibility criteria, participant flow, the measurement procedure, timing details beyond the stated 72 hours timeframe, handling of missing data, analysis populations, statistical models, and any adjustment for participant characteristics. The sample-size description includes planning assumptions, but does not establish the final analyzable sample or the precision of the primary endpoint result.

Safety information is limited to the posted counts. Event descriptions, monitoring duration, attribution, and deaths are not reported in the registry record. These limitations restrict interpretation of both the intended prediction question and the safety information; they do not establish that unreported procedures or analyses were not conducted.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Fetal Fibronectin as a Predictor of Successful Induction of Mid-trimester Abortion — NCT02694198.
• Registry record last updated 2016-05-16; status last verified 2016-04.
• Results first posted 2016-04-06.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry record describes a completed study sponsored by Ain Shams Maternity Hospital, with enrollment of 135, a start date of 2015-09, and a primary completion date of 2016-03. It concerns fetal fibronectin measurement in women undergoing mid-trimester induction of abortion.

The primary outcome is mean cervicovaginal fetal fibronectin level in nanogram per milliliter, with standard deviation and a 72 hours timeframe. The record lists 2 outcome measures but provides no analysis entries or primary outcome results. It does not report a definition of successful induction or a predictive-performance analysis. The posted safety fields list 0 serious adverse events among 135 at risk and 118 other adverse events among 135 at risk; deaths are not reported in the registry record.

The record identifies the study topic and intended measure, but does not support conclusions about the biomarker's observed level, precision, or ability to predict induction success.