Terms of Use

The NIPT/Cell Free DNA Screening Performance Calculator (“Calculator”), also known as "NIPT/cfDNA Performance Calculator", is provided solely for use by healthcare professionals with an understanding of positive predictive value (“PPV”) and negative predictive value (“NPV”). The Calculator is intended to aid such healthcare professionals in counseling their patients about PPV and NPV relative to certain non-invasive prenatal tests (“NIPT”) and the clinical meaning of the patient’s screening results. The Calculator should not be used to provide risk assessment independent of clinical correlation/context and is not intended to replace a health care professional’s best medical judgment based on the clinical circumstances.

The Calculator is provided for educational and informational purposes only, and neither the Genetic Support Foundation (“GSF”) nor the National Society of Genetic Counselors (“NSGC”) approves or endorses any specific values, methods, practices, or sources of information. Use of the Calculator does not create any provider-patient relationship with GSF, NSGC or their respective committee or board members, or Sound Information Services, LLC.

The Calculator uses statistical calculations based on the information provided by the user to determine the predictive values of NIPT/Cell Free DNA Screening utilizing prevalence information based on mateage and population study. The values generated by the Calculator should not be construed as dictating an exclusive course of management, nor does the use of such predictive values guarantee a particular outcome. Proper use of the Calculator requires that the user (i) input accurate data; and (ii) have sufficient understanding of the methodology used and relevance of the results generated. Neither NSGC nor GSF guarantees, or take any responsibility whatsoever for, the accuracy of the results generated by the Calculator.

In consideration of your use of the Calculator, you covenant not to sue, and further waive, release and discharge, NSGC, GSF, and any person and/or organization associated with the Calculator from any and all claims to liability for death, personal injury, or property damage of any kind or nature, whatsoever arising out of, or in the course of, your use of the Calculator. Neither GSF, NSGC, or any other individual, organization or other party involved in the preparation or publication of the Calculator or this website shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any use of or reliance upon the Calculator, the results or values generated by the Calculator or other information or materials included on this website.

Clicking “Accept” constitutes your agreement with the terms set forth above.


NIPT/Cell-Free DNA Screening
Predictive Value Calculator


This calculator will allow you to estimate the Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of prenatal cell-free DNA screening, also commonly referred to as non-invasive prenatal testing (NIPT) or non-invasive prenatal screening (NIPS), based on estimates of population prevalence or by entering your own prevalence numbers. The results of this calculator only apply to patients who have a result from NIPT/cfDNA.

Estimates of NIPT/cfDNA sensitivity and specificity based on a meta-analysis of available studies (Gil et al 2015) are included as default data for some conditions for which NIPT/cfDNA screens. The user may also input the sensitivity and specificity information based on test performance of a specific laboratory. For some conditions, such as microdeletions, there is insufficient data available in the medical literature to determine test performance. The user may wish to contact the specific NIPT/cfDNA lab for sensitivity and specificity information for specific conditions included on NIPT/cfDNA panels.

The calculator utilizes the incidence of trisomy chromosome conditions screened for by the age of the pregnant patient at 16 weeks gestational age. For some conditions, such as 45,X and the microdeletion conditions, the incidence does not vary significantly with the pregnant patient’s age. In some cases, prevalence at gestational ages prior to 16 weeks may be higher, and prevalence at greater than 16 weeks may be lower, given the possibility of spontaneous loss in pregnancies with some chromosome conditions. The prevalence defaults may not be the best estimates of an individual patient’s prior risk for a chromosome condition. Users should be aware that other factors such as ultrasound findings or the results of biochemical aneuploidy screening may affect the estimated prior risk for a chromosome condition for an individual patient and this should be considered when using this calculator. See the FAQs page for more information.