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A not so crystal-clear case.

Case Description


A physician from an outside hospital called our laboratory for help regarding interpretation of cerebrospinal fluid (CSF) results. She was confused by a report from her laboratory that reported the presence of "calcium oxalate crystals 3 + " upon microscopy examination of a CSF sample (Figure 1). The CSF findings were as follows: protein concentration, 0.9 g/L, (reference interval, 0.15-0.35 g/L); chloride, 106 mmol/L (reference interval, 120-130 mmol/L); and glucose, 65 mg/dL (3.5mmol/L) [reference interval, 40-70mg/dL (2.2- 3.9 mmol/L)]. Clinically, the patient presented with features suggestive of acute infective meningitis. There was no current or previous history of toxin ingestion, suicide attempts, arthritis, or renal calculi. Questions

1. What conditions are associated with the presence of oxalate crystals in the CSF?

2. What other simple investigation maybe used to assist with diagnosis?

3. What is the likely cause for the presence of these crystals (given the patient history above)?

The answers are below.


1. Oxalate crystals may occur in the CSF with ethylene glycol poisoning or primary hyperoxaluria type 1. Ethylene glycol is metabolized by alcohol dehydrogenase to form glycolic and oxalic acids.

2. Serum electrolytes and osmolality can be measured, and the anion and osmolar gaps can be calculated. Ethylene glycol poisoning is associated with an increased osmolar gap and increased anion gap metabolic acidosis (1).

3. Staff at the laboratory had used the CSF glucose tube (containing potassium oxalate, which acts as an anticoagulant) for the CSF microscopy analysis.

DOI: 10.1373/clinchem.2011.179713

Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.

Authors' Disclosures or Potential Conflicts of Interest: No authors declared any potential conflicts of interest.

Acknowledgments: We thank the Department of Anatomical Pathology and Cytology, Inkosi Albert Luthuli Central Hospital, for the kind use of their microscope.


(1.) Eder AF, McGrath CM, Dowdy YG, Tomaszewski JE, Ros FM, Wilson RB, et al. Ethylene glycol poisoning: toxicokinetic and analytical factors affecting laboratory diagnosis. Clin Chem 1998;44:168-77.

Verena Gounden [1,2]* and Yashna Rampursat [1,2]

[1] Department of Chemical Pathology, University of KwaZulu-Natal, Durban, South Africa; [2] National Health Laboratory Services, Inkosi Albert Luthuli Central Hospital, Durban, South Africa.

* Address correspondence to this author at: Department of Chemical Pathology, Inkosi Albert Luthuli Central Hospital, 800 Bellair Rd., Cato Manor, Durban 4001, South Africa. Fax +27-31-2402576; e-mail

Received December 1, 2011; accepted January 16, 2012.

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Title Annotation:What Is Your Guess?
Author:Gounden, Verena; Rampursat, Yashna
Publication:Clinical Chemistry
Geographic Code:6SOUT
Date:Aug 1, 2012
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