W HERMANN¹, C GREBHARDT², P MEDINA ESCOBAR^1,2, L RISCH², U NYDEGGER², M RISCH<sup>3

1</sup>Private University Liechtenstein, Triesen, Liechtenstein, ²Labormedizinisches zentrum Dr. Risch, Liebefeld, Switzerland, ³Zentrallabor, Kantonssspital Graubünden, Chur, Switzerland

Background: Measurement of platelet parameters is routinely done to obtain information on hematological, immunological, oncological or infectious disease. Age- and gender independent reference intervals (RI) are commonly used in clinical care of elderly individuals.
Methods: The SENIORLAB study includes subjectively healthy individuals aged 60 or more years. After baseline examination, participants were followed up for overall mortality and morbidity. Age- and gender specific RI were calculated according to the CLSI C28-A3c guideline. Platelet parameters (platelet counts, TC; mean platelet volume, MPV; platelet distribution width, PDW; thrombocrit) were determined with a Sysmex XE-5000 (Sysmex, Horgen, Switzerland). Participants with ferritin <30 U/L ng/ml, CRP >5 mg/L, and death at follow-up were excluded from the analysis.
Results: A total of 1154 individuals aged 60-99 years with a median age of 71, interquartile range, IQR [66,76] were included into the study. Males had significantly lower TC and thrombocrit (p<0.001) as well as significantly higher PDW (p=0.04) than females, whereas no gender difference could be seen in MPV. Both in males and females, TC and thrombocrit were significantly correlated with age, whereas, there was no significant association with MPV and PDW. The RI for TC in males were [90% confidence intervals, CI]: 148 [143-154] - 300 [291-310] x 103/µl at age 60-69, 135 [129-142] – 291 [282-300] x 103/µl at age 70-79, and 129 [121 - 138] – 304 [284-325] x 103/µl at age>80. The respective RI for TC in females were: 168 [163-174] - 358 [345-370] x 103/µl at age 60-69, 166 [161-172] – 344 [334-355] x 103/µl at age 70-79, and 163 [156-171] – 338 [319-355] x 103/µl at age>80. RI for PDW was 10.2 [10.0-10.3] – 16.6 [16.2-16.9] % for males and 10.0 [9.9-10.1] – 16.7 [16.4-17.1] % for females. RI for MPV was 9.3 [9.3-9.4] – 12.5 [12.4-12.6]fl.
Conclusions: Platelet counts and thrombocrit in the elderly shows gender- and age specific reference intervals.