CAPURRO TEST: RATIONALE, TYPES, PARAMETERS, CALCULATIONS, SENSITIVITY - MEDICINE - 2025

The Capurro test is a test used by neonatologists. It is used to calculate the gestational age of the newborn when there is doubt about the date of the last rule. This test allows the newborn to be classified into three categories: preterm, full-term or post-term baby.

A preterm newborn is one born before the normal gestational time of 42 weeks. Specifically, it refers to children born less than 37 weeks. These newborns are also called premature babies.

Pregnant woman and full-term newborn baby. Source: Pixabay / Wikipedia.org

They can be classified as mild (35-36 weeks), moderate (32-34 weeks), and extreme (<32 weeks) premature. Premature infants may have respiratory distress, among other deficiencies, because many of their organs are not yet mature. Example the lungs.

While, a full-term baby is one that is born between 37 to 42 weeks of gestation, that is, it is a neonate who has been born at the time established as normal. In this period of time the baby has completed its development and is ready to face the new environment.

Finally, a baby born post-term means that the gestation time has exceeded 42 weeks. In many countries it is popularly said: "The delivery is over."

The Capurro method takes into consideration the analysis of 4 physical and 2 neurological parameters (Capurro A) or only 5 physical parameters (Capurro B).

Basis

The Capurro test is based on the calculation of gestational age through the analysis of certain parameters.

The parameters to be evaluated, according to the original method of Dubowitz et al, consisted of a number of physical and neuromuscular characteristics.

Later Ballard summarized them in 6 somatic and 6 neurological characteristics and, finally, Capurro summarized them in 4 physical and 2 neurological parameters (Capurro A) or only 5 physical parameters (Capurro B).

In any case, other methods have subsequently emerged, such as Ballard's New Score test, who refined the parameters, managing to determine the gestational age in extremely premature infants.

According to Capurro, in those neonates who are not in conditions to be evaluated from the neurological point of view, this step is simply ignored and a physical parameter is added to the 4 existing ones.

The parameters that are evaluated (Capurro A or B) provide the information necessary to estimate gestational age and allow the newborn to be classified as premature, term or post-term.

Capurro test types

There are 2 types of Capurro test. The Capurro A test and the Capurro B test.

The Capurro A test

It is applied to newborn children who do not have any impediment to be examined and who do not show any neuromuscular damage due to trauma, anesthesia or infection.

The Capurro B test

It is applied in newborn children who have a condition that makes it impossible to be examined. For example, newborns who are critically ill and have a central line taken or have had to be intubated, or have neuromuscular problems.

For the test to be applicable, the newborn must weigh more than 1,500 grams.

Parameters used by the Capurro A test

Physical

Shape of the pinna, diameter of the mammary gland, skin texture, and the characteristics of the plantar folds.

Neurological

The sign of the scarf and the fall of the head.

Capurro B test parameters

Neurological signs are ignored and only the aforementioned physical parameters are evaluated and the formation of the nipple is attached to these.

Physical and neurological characteristics to observe in the Capurro test and scoring system.

- Physical

Shape of the pinna

In this case, the neonatologist stands in front of the newborn and observes the upper part of the newborn's pinna. Specifically, you will see if it protrudes forming a kind of roof.

Later, you will move the child's head from side to side to visualize the accentuation of the curvatures. During the evaluation the pavilion should not be touched, only seen.

The observed characteristics are scored as follows:

- Flattened flag without curvature: 0 points.

-Partially curved edge on top: 8 points.

-Top edge curved in its entirety: 16 points.

-The entire curved ear: 24 points.

Diameter of the mammary gland

The neonatologist will touch the mammary glands of the newborn, specifying very well how far the breast tissue reaches. The physician should identify the boundary with the subcutaneous tissue of the skin. Then you will carefully measure the diameter of the breast tissue, using a tape measure.

It is dotted as follows:

-Non-palpable: 0 points.

-Diameter <5 mm: 5 points.

-Diameter between 5 - 10 mm: 10 points.

-Diameter> 10 mm: 15 points.

Nipple formation (only used in the Capurro B test)

In this parameter, the diameter of the nipple will be measured with the tape measure.

-Barely visible without areola: 0 points.

-Nipple smaller than 7.5 mm with smooth and flat areola: 5 points.

-Nipple> 7.5 mm with pointed areola and non-raised edge: 10 points.

-Nipple> 7.5 mm with pointed areola and raised edge: 15 points.

Skin texture

The specialist will examine the baby's skin, looking for signs of flaking or cracking. In particular, it will explore the skin on the forearms, legs, back of the hands, and feet.

It is valued as follows:

-Very fine and gelatinous skin: 0 points.

-Smooth and fine leather: 5 points.

-Slightly thicker skin with little flaking: 10 points.

-Thick skin with certain superficial cracks and significant flaking, both hands and feet: 15 points.

-Thick skin and very deep cracks. Parchment Cracks: 20 points.

Folds of the soles of the feet

The grooves and folds they present should be observed on the soles of the feet. These are easily recognizable. Both feet of the baby are taken and the skin of the sole is spread as far as possible. The furrows disappear when the skin is spread, while the folds are marked.

According to the furrows observed, it is valued as follows:

-Without folds: 0 points.

-Poor definition of marks in the previous half: 5 points.

-Very well defined marks with grooves, both in the anterior half of the sole of the foot: 10 points.

-Surcos in the anterior half of the sole of the foot: 15 points.

-Surcos in more than the anterior half of the sole of the foot: 20 points.

- Neurological

Scarf sign

Measures axial and scapular muscle tone. The newborn's hand is carefully taken and passed over the thorax, reaching up to the neck in the form of a scarf. The position of the elbow should be observed by comparing it with the midline.

Punctuation:

-The elbow is located on the opposite axillary line: 0 points.

-The elbow is located between the axillary line of the opposite side and the midline: 6 points.

-The elbow is located in the middle line: 12 points.

-The elbow is located in the axillary line on the same side: 18 points.

Head drop sign

It measures the tone of the cervical muscles, also assesses the neurological maturity of the newborn.

Assessment:

-Head fall completely backwards: 0 points (angle> 270 °).

-Head drop at an angle between 180 ° - 270 °: 4 points.

-Head drop at an angle of 180 °: 8 points.

-Head fall at an angle <180 °: 12 points.

Capurro Test Calculations

As has already been seen, there is an evaluation system where the possibilities of responses to each parameter are reflected and each one has a score. This evaluation system is the product of numerous investigations.

At the end, the accumulated points are added according to the observed characteristics and the corresponding formula is applied, as the case may be.

In the case of the Capurro A method

Estimated gestational age = (200 + cumulative score) / 7 days of the week

In the case of the Capurro B method

Estimated gestational age = (208 + cumulative score) / 7 days of the week

General formula (average of both)

Estimated gestational age = (204 + accumulated score) / 7 days of the week

In all cases the result is obtained in weeks.

Graph to calculate gestational age in weeks, according to the Capurro method

Another way to calculate gestational age by the Capurro method is using the following graph.

Graph to calculate gestational age in weeks: Source: (Cerezo R. 1976), cited in Protocol for the Care of the Low-Risk Newborn. Part 5. Ministry of Health. 221: 249. Graphic Design MSc. Marielsa gil

In it, the score obtained in the 5-parameter test (Capurro B) is located and it is extrapolated to obtain the weeks of gestation, without using any formula.

Sensitivity and reliability of the Capurro method

The Capurro method, in general, is useful for newborns 29 weeks and older. In fact, this method has low sensitivity when evaluating gestational age in premature infants.

Keep in mind that even though this method is widely used, it is not infallible, as some parameters are very subjective. Therefore, the method has a margin of error of approximately ± 8 to 9 days. The error can increase if the evaluator has little experience.

In this sense, Ventura believes that the Capurro method has a tendency to overestimate the gestational age of the newborn. He came to this conclusion after comparing Capurro's method against running ultrasounds from 10 + 0 to 14 + 2 weeks.

On the other hand, Salamea and Torres compared the modified Ballard and Capurro method against the date of the last menstruation (LMP) and determined that both methods had a good correlation, 72% and 64% respectively.

They also determined that there are better correlation results with newborns of the female sex and with babies weighing 3,500 grams and above.

All of this leads to the reflection that the gold standard for assessing gestational age is the last date of menstruation or early ultrasound control.

References

1. Ventura W. Validity of postnatal evaluation of gestational age: comparative study of the Capurro method versus ultrasound at 10 + 0 to 14 + 2 weeks. Peru. gynecol. obstet. 2015; 61 (2): 115-120. Available at: scielo.org.
2. Low Risk Newborn Care Protocol. Part 5. Ministry of Health. 221: 249. Available at: paho.org
3. "Capurro test." Wikipedia, The Free Encyclopedia. 16 May 2018, 10:22 UTC. 9 Aug 2019, 22:23 org.
4. Salamea J, Torres M. “Gestational age estimation using the Ballard and Capurro methods compared with the date of the last reliable menstruation, in term and post-term newborns, at the Vicente Corral Moscoso Hospital. Cuenca 2014 ”. 2015. Thesis to qualify for the Medical degree. Ecuador. Available at: dspace.ucuenca.edu.ec
5. Gómez M, Danglot C, Aceves M. Classification of newborn children. Rev Mex Pediatr 2012; 79 (1); 32-39. Available at: medigraphic.com