When Platelet Counts are High
- Thrombocytosis in Systemic Lupus Erythematosus: A Possible Clue to Autosplenectomy?
- Journal of Rheumatology, Volume 34, Number 7, July 2007, pp. 1497-1501
What is the topic?
The spleen is an important organ in both the body’s immune system and its blood circulation. The spleen makes antibodies that protect against infections. It also filters the blood, removing old and damaged red blood cells. In some medical conditions the spleen can be damaged, and this can increase the risk for infections. This is sometimes seen in lupus patients, though this is rare.
What did the researchers hope to learn?
The researchers wanted to see if there were specific lupus symptoms that showed up more often in patients whose spleens weren’t functioning well. They were particularly interested in lupus patients with an unusually high number of platelets. Platelets are components of blood cells that can stick together to form clots at wounds, and thus help stop the loss of too much blood when an injury occurs. High platelet counts are much less common in lupus patients than low platelet counts.
Who was studied?
The researchers studied 465 consecutive lupus patients at a rheumatology clinic in Italy. All of the patients -- 387 women and 78 men -- were Caucasian and over 20 years of age.
How was the study conducted?
Blood samples from each of the patients were tested for antibodies and platelet counts over a period of years. Patients who had high platelet counts in 3 consecutive blood draws taken 3 months apart were further studied with an additional kind of test called a blood smear, which could detect signs of spleen problems. If the blood smear was abnormal, the patients had imaging studies, including ultrasound exams and CT scans to determine whether their spleens were damaged. Twenty patients who did not have high platelet counts also had blood smear tests done in order to compare the results.
What did the researchers find?
Of the 465 patients studied, 16 women and 1 man were diagnosed with thrombocytosis, and this diagnosis came when their lupus disease was inactive. When the blood smears were done on these patients, three showed signs that their spleen was not functioning properly, and this was confirmed by ultrasound and CT scans. Each of these three patients had antiphospholipid antibodies (aPL), which have been linked to blood clots. One of these three patients developed high platelet counts after previously having abnormally low platelet counts. None of the 20 blood smears from control patients with normal platelet counts showed any indication of spleen problems.
To the researchers these findings suggested that when lupus patients have high platelet counts, the damage to the spleen could be caused by blood clots related to antiphospholipid antibodies. They recommended that lupus patients who have high platelet counts should be examined for these antibodies.
What were the limitations of the study?
While 3 of the 17 patients with high platelet counts were determined to have spleen problems, fourteen others did not. So most people with high platelet counts do not have problems in the spleen. Also, even in those three patients, there was no way to determine if the spleen problems occurred before or after the patients developed high platelet counts.
What do the results mean for you?
The spleen plays a very important role in fighting bacterial infections, so even though only a minority of patients with elevated platelet counts have spleen problems, this is the group that should be further tested to see if their spleen is functioning properly. This may be particularly important in lupus patients who had previously been diagnosed with thrombocytopenia (low platelet counts) and then show up with thrombocytosis (high platelet counts).
Also, since all three of the patients who had spleen damage had aPL, doctors whose lupus patients have aPL may want to keep an eye out for changes in platelet counts as a sign of potential spleen damage.