Platelet counts in patients with rheumatoid arthritis at the Kenyatta National Hospital, Nairobi, Kenya
Background: Rheumatoid arthritis (RA) is a disease associated with significant morbidity and mortality. Thrombocytosis is one of the haematological manifestations of rheumatoid arthritis that occurs in active disease. Platelet counts may vary depending on disease activity. The variation has been shown to correlate with clinical and laboratory indices of disease activity in RA. Occasionally patients with RA may have drug induced thrombocytopenia. Objectives of the study: To determine the relationship between platelet counts and clinical disease activity in patients with RA at Kenyatta National Hospital (KNH). Study design and setting: A cross-sectional descriptive study conducted in patients with RA attending the KNH Rheumatology Outpatient Clinic (ROPC). Methods: Patients presenting to the clinic were screened and those meeting the inclusion criteria recruited into the study. Consecutive sampling technique was done. A targeted history was obtained, following which a physical exam was done on the recruited patients. The patients' platelet counts were measured using Abbot Cell Dyn 1300 counter. The patients' erythrocyte sedimentation rate (ESR) was measured using the Wintrobe's method. The . patients' clinical disease activity was assessed using the DAS 28 score and recorded. RESULTS: One hundred and four patients were recruited over the 6 months period between November 2010 and April 2011. Females were 90(86.5%) and 14(13.5%) were males giving a male to female ratio of 1 :6.4. The mean age of the patients was 48years. Regarding medication use, 75% of the patients were on disease modifying anti-rheumatic drugs (DMARDs), 72.1 % on non-steroidal analgesics (NSAIDs) and 46.2% on steroids. The mean platelet count was 313.2 ﾱSD94 x 109/L with a range of 152-611 x 109/L. Only 15 (14.4%) had thrombocytosis (>400x 109 /L). No case of thrombocytopenia was recorded. Ninety two patients had active disease (88.5%) while 10 (11.5 %) were in remission. Among those with active disease, 10(9.6%) had mild disease, 51 (49%) moderate disease and 31 (29.6%) high disease activity. The DAS28 score was not significantly different between those who had thrombocytosis and those who had normal platelet counts (p=0.413). However, HB, MCV and MCH were significantly lower in those with thrombocytosis (P = 0.02, 0.002, 0.03 respectively). No correlation was found between platelet counts and clinical disease activity (DAS28). Conclusion. The prevalence of thrombocytosis was less than that reported in majority of the studies in other set-ups. Platelet counts are poor indicators of disease activity in our patients with RA as no relationship was found between platelet counts and disease activity in patients with RA in KNH.