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Are radiologists good at detecting rickets?

Posted on: May 16, 2018   by  John Cannell, MD

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Imagine your infant is fussy, not gaining weight, sweat pours from his head and he often screams like something is hurting him. Say you are one of the few people in the world that knows excessive sweating is a very specific sign of vitamin D deficient rickets. So, you bring him to the doctor who orders x-rays of his wrist. The radiologist says his x-rays are normal, but your infant is still displaying signs of pain. What could be the problem? The problem lies with the diagnostic procedure.

Are x-rays an accurate method of diagnosing rickets?

Are x-rays good at diagnosing metabolic bone diseases such as rickets? If you think they are, you are saying x-rays have a high sensitivity and specificity. [Sensitivity is the ability of a test to correctly identify a disease (true positive rate), whereas specificity is the ability to correctly identify those without the disease (true negative rate)].

If radiology was good at diagnosing rickets, wouldn’t they have published this fact? Historically, bone biopsy – not radiographs – is the gold standard for diagnosing metabolic bone disease. I diligently searched the radiological literature, but I could find no scientific support for the use of x-rays as a tool for diagnosing rickets. However, I did find an abundance of evidence that radiologists often miss metabolic bone diseases, such as rickets.

For example, researchers at Columbia studying metabolic bone disease that can occur with kidney failure concluded that even with state-of-the-art CT scans, radiology is insufficient in diagnosing metabolic bone disease and requires bone biopsy.[1]  Likewise, in Japan, bone biopsy “is used for the diagnosis and the assessment of treatment response in rickets.” [2] Even in domestic animals, “(bone rachitic) diagnoses based on clinical signs and radiology are unreliable.” [3] Rauch states, “children . . .with severe bone fragility should have a bone biopsy for diagnostic purposes.” [4]

Reliability of x-rays for diagnosing metabolic bone disease

In terms of reliability, a small but growing number of physicians now realize that radiology is quite subjective. For example, when radiologists assessed their ability to detect and grade metabolic bone disease, their inter-rater reliability was as low as .012[5] (inter-rater reliability is a measure of agreement between different radiologists reading the same films. It ranges from 0 to 1 with 1 being perfect agreement between radiologists and 0 being no agreement). Likewise, Silva et al. also found poor inter- and intra-observer reliability rates for x-ray diagnosis of metabolic bone disease.[6]

Any claim that radiology is the gold standard for detection of rickets, is simply not true. In writing about metabolic bone disease, such as rickets, a current textbook of orthopedic pathology states, “In subtle cases, absolute certainty require tissue examination” (pp. 104). [7]

Are bone biopsies a better option?

The best, but saddest, way to know if radiologists can accurately diagnose rickets is when the infant dies and has an autopsy, which involves a bone biopsy. That will compare the accuracy of the x-rays before death compared to the bone biopsy after death.

Cohen et al 12 reported on biopsy-proven rickets in autopsies of 13 of 15 infants <1-year age, in which two pediatric radiologists missed 84% of the rickets cases. Even when they reviewed the radiographs of the corpses retrospectively, with the rachitic histology in hand, the radiologists could not see any rachitic changes.[8]

At least five additional autopsy studies have found radiologists miss biopsy-proven rickets more often than not.[9], [10], [11], [12], [13] The most recent and largest of the five studies showing that radiologists routinely miss infantile rickets is the 2014 study by Scheimberg and Perry who analyzed 52 postmortem cases (aged 2 days to 10 years).They found rickets in 18 ricket cases, but radiologists only identified 20% of the rickets.

Final thoughts

Overall, looking at all six studies, and they are the only ones I can find, it appears radiologists are simply unable to accurately diagnose rickets. But, almost no radiologists know this. So, if you worry your child may have rickets, don’t bother getting x-rays. Simply give the child both calcium (10 mg/lb. body weight) and vitamin D (150 IU/ lb. body weight).

In rickets, one must forget what the radiologists say. The tragedy is the thousands of families that are having their infants removed from their home by Child Protective Services because the radiologists are missing rickets on a wholesale basis.

Citation

Cannell, JJ., MD. Are radiologists good at detecting rickets? The Vitamin D Council Blog & Newsletter, 4/2018.

References

[1] Babayev R, Nickolas TL.  Can one evaluate bone disease in chronic kidney disease without a biopsy? Curr Opin Nephrol Hypertens. 2014 Jul;23(4):431-7.

[2] Ito A, Yajima A. Is bone biopsy necessary for the diagnosis of metabolic bone diseases? Necessity of bone biopsy]. Clin Calcium. 2011 Sep;21(9):1388-92. doi: CliCa110913881392. Review. Japanese. (Article in Japanese, abstract only)

[3] Dittmer KE, Thompson KG. Vitamin D metabolism and rickets in domestic animals: a review. Vet Pathol. 2011 Mar;48(2):389-407. doi: 10.1177/0300985810375240. Review.

[4] Rauch F. Bone biopsy: indications and methods. Endocr Dev. 2009;16:49-57.

[5] Takedani H, Fujii T, Kobayashi Y, Haga N, Tatsunami S, Fujii T. Inter-observer reliability of three different radiographic scores for adult haemophilia.Haemophilia. 2011 Jan;17(1):134-8.

[6] Silva M, Luck JV Jr, Quon D, Young CR, Chin DM, Ebramzadeh E, Fong YJ.Inter- and intra-observer reliability of radiographic scores commonly used for the evaluation of haemophilic arthropathy. Haemophilia. 2008 May;14(3):504-12.

[7] Vigorita, V. Orthopedic Pathology, 2nd edition, Chapter 3, Metabolic Bone Disease, 2007, Lippincott Williams & Wilkins, New York.

[8] Ayoub D. Limitations of radiology in rickets. Letter to editor: Pediatr Dev Pathol. 2013 Sep-Oct;16(5):397

[9] Scheimberg I, Perry L. Does low vitamin D have a role in pediatric morbidity and mortality? An observational study of vitamin D in a cohort of 52 postmortem examinations. Pediatr Dev Pathol. 2014 Nov-Dec;17(6):455-64.

[10] Cohen MC, Offiah A, Sprigg A, Al-Adnani MU.  Vitamin D deficiency and sudden unexpected death in infancy and childhood: a cohort study. Pediatr Dev Pathol. 2013 Apr 19.

[11] Liu D. Pathological and X-ray study on bony specimens of rickets from 124 fetal and infantile autopsies. Zhonghua Yi Xlle Za Zhi 1991: 71: 385-7. (Article in Chinese, abstract only)

[12]Ladhani S, Srinivasan L, Buchanan C, Allgrove J.  Presentation of vitamin D deficiency. Arch Dis Child. 2004 Aug;89(8):781-4.

[13] Follis, RH, Jackson D, Eliot MM and Park EA. The prevalence of rickets in children between two and fourteen years of age. AM J DIs Child 66(1): 1-11, 1943.

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