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Q&A column, 3/15

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Editor: Frederick L. Kiechle, MD, PhD

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Using RBC parameters to rule out beta thalassemia trait

Seminal fluid coagulation

Q. Are red blood cell parameters (Hb, MCV, MCH, MCHC, and RDW), especially a normal MCV, a reliable screening tool for ruling out beta thalassemia trait? Is the sickle solubility test reliable in ruling out sickle cell disorder?

A. Population screening schema for hemoglobinopathies and thalassemias encompass detailed knowledge of the predictive value of the test or tests employed. Predictive value varies according to the prevalence of the disorder in the screened population and the sensitivity and specificity of the particular tests. Different populations and jurisdictions will have varying needs according to these parameters in fulfilling the fundamental aims of the screening program.

In general terms, in screening for thalassemia, the red blood cell para-meters should be evaluated in conjunction with the prevalence of hemoglobinopathies/thalassemias in the patient’s ethnic group and with the patient’s clinical and familial history. In ethnicities where there is a high prevalence of thalassemia and abnormal hemoglobin variants, additional techniques to investigate the presence of these conditions (high-performance liquid chromatography or electrophoresis) may be warranted. This will enable a more timely detection of clinically significant disorders.

All positive and negative sickle solubility tests should be confirmed by an alternative method. If positive, an alternative method is also necessary to distinguish sickle cell trait from sickle cell disease and other compound heterozygous conditions. False-positives have been described in patients with high plasma protein levels, including multiple myeloma. False-negatives are seen if the percentage of hemoglobin S is below 15 percent, if the concentration of fetal hemoglobin is high, or if the total hemoglobin is less than 8 g/dL. This test is not recommended in infants before six months of age because of the high concentration of Hb F in this age group. Some variants (i.e. Hb D-Punjab, Hb O-Arab) that could result in clinically significant sickle cell disorders if paired with Hb S in offspring would not be detected by sickle solubility testing (or RBC parameters).

Ryan K, Bain BJ, Worthington D, et al.; British Committee for Standards in Haematology. Significant haemoglobinopathies: guidelines for screening and diagnosis. Br J Haematol. 2010;149(1):35–49.

Janet Piscitelli, MD, Medical Director, East Region Quest Diagnostics, Teterboro, NJ, Former member, CAP Hematology/Clinical Microscopy Resource Committee, Member, CAP ChemistryResource Committee

Jennifer L. Oliveira, MD, Co-director, Metabolic Hematology Laboratory, Mayo Clinic,
Rochester, Minn., Member, CAP Hematology/Clinical Microscopy Resource Committee

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Q. The absence of coagulation of seminal fluid has been attributed to bilateral congenital absence of the vas deferens and seminal vesicles due to the absence of the coagulation substrate (fibrinogen-like precursor). What is the significance of the absence of coagulation of seminal fluid in a patient who previously experienced normal seminal fluid coagulation followed by normal liquefaction, and had fathered children? Are there medications that can prevent seminal fluid coagulation? Are there pathologic processes—carcinoma, for example—that can affect the prostate gland and prevent seminal fluid coagulation (possibly due to an increase in enzymes of prostatic origin such as acid phosphatase), causing a localized acceleration of the fibrinolytic process?

A. I discussed this at length with our urologic specialist and another teaching faculty physician, and they agree that the coagulation/liquefaction are often variable within multiple samples from any single patient for reasons currently unknown. While men with prostate cancer often exhibit absence of coagulation, it is not necessarily an indicator of that cancer. Anecdotally, several medications have been observed to interrupt coagulation or liquefaction—some antidepressants, antihistamines, and a few others. In the case of a patient who had previously fathered children, neither physician felt this alone was reason for concern.

In the end, the lack of coagulation is not a clinical concern to either physician in routine care. The patient should be able to produce children with assisted reproductive technology in the case of congenital bilateral absence of the vas deferens.

Kepler Johnson IV, ELD, Embryology Laboratory Director,
Mid-Iowa Fertility, Clive, Iowa, Member, CAP Reproductive Medicine Committee

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