Normative Clinical Reference for Intima-media Thickness of Carotid Arteries among Nigerian Adults

The intima-media thickness (IMT) of the carotid arteries is said to be predictive of the risk of cerebrovascular accidents in patients and said to be affected by sex, age, and race. The lack of normative reference values of carotid IMT can adversely affect the screening of subclinical atherosclerosis in Nigeria. Sonography is the most widely used tool in clinical practice for IMT determination.

This study was aimed at obtaining sonographic reference values of the IMT of the carotid arteries of healthy adult Nigerians for clinical use.

This is a prospective study, where participants were selected by a simple random technique.

The study was carried out in 2019 on adult Nigerians from different ethnic backgrounds that resided in Bayelsa State.

The study population was 104 healthy Nigerian adults both male and female between 18 and 64 years of age. Excluded were those without informed consent, Nigerians aged below 18 and above 65 years, anyone with a history of cardiovascular, cerebrovascular, or metabolic disorders, and athletes. After confirming normal blood pressure and taking their physical measurements, participants' necks were scanned with an "EcoMed" ultrasound machine version VERTU-3 Portable USG with a linear transducer and a frequency of 7.0 MHz by an experienced radiologist.

The IMT was recorded for the subjects in millimetres where common carotid artery: males = 0.487 ± 0.014, females = 0.480 ± 0.010 with a reference range of 0.200-0.750 mm; internal carotid artery: males = 0.500 ± 0.019, females = 0.459 ± 0.013 with a reference range of 0.200-0.750 mm; external carotid artery: males = 0.479 ± 0.018, females = 0.437 ± 0.014 with a reference range of 0.180-0.780 mm. The values for the males were higher than those of the females; however, they were not statistically significant. There was also no statistically significant difference between right and left sides in the IMT despite the right persistently being higher than the left in the general study population.

This study has been able to provide reference values for IMT of the carotid arteries among Nigerians for clinical use in the meantime. We believe that a systematic review of similar data can further be done for the standardisation of national reference.